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Synergistic Bimetallic PdNi Nanoparticles: Enhancing Glycerol Electrooxidation While Preserving C3 Product Selectivity
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ACS Applied Energy Materials

Cite this: ACS Appl. Energy Mater. 2024, 7, 5, 1802–1813
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https://doi.org/10.1021/acsaem.3c02789
Published February 29, 2024

Copyright © 2024 The Authors. Published by American Chemical Society. This publication is licensed under

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Abstract

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Electrochemical conversion of glycerol offers a promising route to synthesize value-added glycerol oxidation products (GOPs) from an abundant biomass-based resource. While noble metals provide a low overpotential for the glycerol electrooxidation reaction (GEOR) and high selectivity toward three-carbon (C3) GOPs, their efficiency and cost can be improved by incorporating non-noble metals. Here, we introduce an effective strategy to enhance the performance of Pd nanoparticles for the GEOR by alloying them with Ni. The resulting PdNi nanoparticles show a significant increase in both specific activity (by almost 60%) and mass activity (by almost 35%) during the GEOR at 40 °C. Additionally, they exhibit higher resistance to deactivation compared to pure Pd. Analysis of the GOPs reveals that the addition of Ni into Pd does not compromise the selectivity, with glycerate remaining at around 60% of the product fraction and the other major product being lactate at around 30%. Density functional theory calculations confirm the reaction pathways and the basis for the higher activity of PdNi. This study demonstrates a significant increase in the GEOR catalytic performance while maintaining the selectivity for C3 GOPs, using a more cost-effective nanocatalyst.

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Introduction

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In recent years, biodiesel has emerged as a promising biofuel derived from vegetable oils, animal fat, and their residues. (1,2) The production of biodiesel generates glycerol (Gly) as a significant byproduct, accounting for approximately 10 wt % of the biodiesel produced. (3) The global growth of the biodiesel industry has resulted in a surplus of Gly, causing its market price to decline. (4,5) Consequently, there is growing interest in converting this excess Gly into commercially valuable chemicals. One promising approach for Gly valorization is through the Gly electrooxidation reaction (GEOR), which enables the simultaneous production of valuable chemicals on the anode from Gly and hydrogen on the cathode with lower energy requirements than conventional water electrolysis. (5)
Non-noble and noble metal-based bimetallic and trimetallic electrocatalysts have shown remarkable results for the GEOR by achieving higher activity than the monometallic counterparts. (6−10) Among these, Pd-based nanocatalysts exhibit great potential for the GEOR due to their outstanding performance in alkaline environments, similar cost and abundance to Pt, (11) and lower susceptibility to CO poisoning. (12) Although in the monometallic form, non-noble transition metals such as Ni require a significantly higher potential than Pd to electrochemically oxidize Gly; (13) the addition of such metals to noble metals can significantly enhance the catalytic activity and stability for the GEOR. (11,14−16) Further approaches to improve the catalytic performance of nanomaterials include tuning their morphology and increasing the surface area by introducing porosity or reducing the particle size. (17) The use of PdNi nanocatalysts extends beyond the GEOR to the electrooxidation of other biomass derivatives and organic molecules such as formic acid, (18,19) ethylene glycol, (20) carbohydrazide, (21) ethanol, (22−25) and methanol. (26−28) Aside from nanocatalysts, electrodeposited PdNi films have also been studied for the electrooxidation of lactic (29) and gluconic acids. (30)
The role of Ni in PdNi catalysts in enhancing the electrooxidation of alcohols has been mainly studied for ethanol (25,31,32) and methanol. (27) For ethanol oxidation, the presence of Ni significantly increased the current density compared to pure Pd when Ni served as the surface layer of sputtered PdNi catalysts, in contrast to when it was placed at the sublayer. (32) These findings were supported by density functional theory (DFT) calculations, which assessed the impact of varying the percentage of surface Ni on a PdNi catalyst with (111) facets. (23) These studies highlight the importance of the structural design of PdNi catalysts. For methanol oxidation, a combined experimental and DFT study revealed that increased Ni concentrations in PdNi nanocatalysts, and specifically Pd0.5Ni0.5 (at. %), led to higher selectivity toward CO2 formation, suppressed CO poisoning, and improved activity for methanol electrooxidation. (27)
For the GEOR, Pd0.5Ni0.5 (at. %) nanoparticles (NPs) have shown a higher current density than Pd NPs, (11) which aligns with the general consensus that Pd0.5Ni0.5 (at. %) represents the optimal Pd/Ni atomic ratio for Pd-rich catalysts. (14,15) Nevertheless, there is still much to explore regarding the formation of glycerol oxidation products (GOPs) using PdNi electrocatalysts. In alkaline media, Pd-based catalysts typically yield products such as glyceric acid/glycerate (GLA), tartronic acid/tartronate (TTA), oxalic acid/oxalate (OA), glycolic acid/glycolate (GA), and formic acid/formate (FA). (7) However, there are limited reports quantifying GOPs produced by PdNi catalysts. (33) FA, GA, and OA, formed through C–C bond cleavage, are believed to occur at high oxidation potentials, (34) but adsorbed CO has been observed at potentials below the onset of the GEOR on Pd and PdNi nanocatalysts, indicating C–C bond cleavage from a dissociative Gly adsorption step at low potentials. (11) Both scenarios are undesirable because the three carbon (C3) GOPs GLA, LA, and TTA are more valuable due to their uses in important industries such as biomedical (GLA and TTA) and pharmaceuticals (LA), (35) making the mitigation of C–C bond cleavage a primary aim in GEOR developments.
While the typical synthesis of PdNi nanocatalysts involves methods such as coprecipitation, sputtering, electrodeposition, and others, the alloying process can be challenging due to the need for high temperatures, particular additives and reductants, pH adjusters, and multistep synthetic procedures. (36−38) Herein, we report the catalytic performance for the GEOR in alkaline media of sub-10 nm Pd and PdNi NPs, obtained via a modified one-step metal reduction synthesis in organic medium (39) and characterized by transmission electron microscopy (TEM) and powder X-ray diffraction (PXRD). The Pd and PdNi NPs were deposited onto carbon paper electrodes (Pd/C and PdNi/C, respectively), and their electrocatalytic activity was studied by cyclic voltammetry (CV) and iR-corrected polarization curves (ICPCs). Galvanostatic electrolysis was employed to generate GOPs, and the product distribution was determined via high-performance liquid chromatography (HPLC), with 90% of the product fractions containing C3 GOPs. DFT calculations confirmed similar reaction pathways for GEOR on Pd(111) and PdNi(111). PdNi/C outperformed Pd/C in terms of both mass and specific activity while exhibiting minimal differences in the distribution of the GOPs. Our study demonstrates the promising performance of PdNi NPs in GEOR by maintaining selectivity for C3 products similar to that of Pd while enhancing the electrocatalytic activity and reducing the overall catalyst cost through a reduction in the required amount of Pd.

Experimental Section

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Materials and Reagents

Palladium(II) acetylacetonate (Pd(acac)2, Sigma-Aldrich, 99%), nickel(II) acetylacetonate (Ni(acac)2, Combi-Blocks Inc., 98%), oleylamine (OAm, Sigma-Aldrich, technical grade, 70%), borane tert-butylamine (BTB, Alfa Aesar, 97%), 1-octadecene (ODA, Sigma-Aldrich, for synthesis), acetone (Honeywell, ≥99.5%), and ethanol (absolute, VWR Chemicals, ≥99.7%) were used for the catalyst synthesis. For the GEOR experiments, the carbon fiber paper (H23, thickness 210 μm, Freudenberg) was cut into 1 cm2 pieces before hydrophilic treatment. Analytical-grade sodium hydroxide (NaOH, Merck) and Gly (Merck) were both purchased from VWR (Radnor, PA, USA). The ultrapure water (18 MΩ) used to prepare all solutions was obtained with a Millipore DirectQ3 purification system from Millipore (Burlington, MA, USA).

Electrochemical Instrumentation

A Princeton Applied Research PAR273A potentiostat/galvanostat from AMETEK (Minneapolis, MN, USA) was used for electrochemical measurements. To record ICPCs, a current interrupt method was used through the PAR273A in connection with a National Instruments (NI) cDAQ-9178 chassis and a NI9223 voltage digitalizer (Austin, TX, USA), as reported previously. (40) A Hg/HgO reference electrode (RE) (RE-A6P, BioLogic, 1.0 M NaOH) was used for all of the measurements.

Synthesis of Pd and PdNi Electrocatalysts

Pd and PdNi NPs were synthesized via the reduction of Pd(acac)2 and coreduction of Pd(acac)2 and Ni(acac)2, respectively, in an organic medium with OAm serving as a surfactant, BTB as a reducing agent, and ODE as a solvent (see Scheme 1).

Scheme 1

Scheme 1. Schematic Representation of the Pd and PdNi Nanoparticle Synthesis
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Synthesis of Pd Nanoparticles

Pd NPs were synthesized using a modified previously reported procedure. (39) A metal-precursor mixture containing 150 mg of Pd(acac)2 (ca. 0.5 mmol) in 30 mL of OAm in a 50 mL round-bottomed flask equipped with a rubber septum was flushed with argon gas for 30 min to remove excess oxygen. After that, the mixture was heated to 90 °C under magnetic stirring (800 rpm) and an argon atmosphere until it became homogeneous. Next, a reductant-solvent mixture of 600 mg of BTB and 6 mL of OAm, preheated at 60 °C, was quickly injected into the metal-precursor mixture with a syringe. The resulting reaction mixture was allowed to react for 1 h under the same stirring rate and argon stream. The resulting solution was washed by centrifugation four times with an acetone/ethanol mixture (7:3) at 12,000 rpm for 15 min, followed by final redispersion in 1 mL of ethanol and vacuum drying at 60 °C for 24 h.

Synthesis of PdNi Nanoparticles

PdNi NPs were synthesized using a modified previously reported procedure. (39) A reductant-solvent mixture containing 400 mg of BTB, 6 mL of OAm, and 14 mL of ODE in a 50 mL round-bottomed flask equipped with a rubber septum was flushed with argon gas for 30 min to remove excess oxygen. After that, the mixture was heated to 90 °C under magnetic stirring (800 rpm) and an argon atmosphere until it became homogeneous. Next, a metal-precursor mixture of 38.08 mg of Pd(acac)2 (0.125 mmol) and 128.46 mg of Ni(acac)2 (0.300 mmol) in 6 mL of OAm, preheated at 60 °C, was quickly injected into the reductant-solvent mixture with a syringe. The resulting reaction mixture was allowed to react for 1 h under the same stirring rate and argon stream. Finally, the resulting solution was washed, redispersed, and dried similarly to that of the Pd NPs.
The excess Ni precursor introduced in solution is due to the tendency of Pd to be reduced much more readily than Ni. Therefore, to incorporate the desired amount of Ni into the PdNi bimetallic catalyst, a higher Ni content than Pd is required. Since the main goal was to study the performance of PdNi NPs with a Pd/Ni ratio of 1:1, the synthetic procedure was not further optimized to compensate for the losses. The optimization can therefore be a basis for future work and synthetic strategy improvement. Additionally, if the remaining Ni was simply discarded, it would decrease the cost-effectiveness and greenness of the catalyst synthesis process; however, the remaining Ni could easily be recovered as pure Ni through electrodeposition or another reduction process.

Characterization of Electrocatalysts

TEM imaging and energy-dispersive X-ray spectroscopy (EDS) were carried out on a JEOL JEM-2100F microscope operating at an acceleration voltage of 200 kV. TEM samples were prepared by depositing ∼20 μL of NP dispersion in ethanol on a 300-mesh ultrathin Lacey carbon-supported gold grid and allowing the solvent to evaporate. PXRD was performed on a Bruker D8 DISCOVER diffractometer using a Cu Kα X-ray source (λCuKα1 = 1.540598 Å and λCuKα2 = 1.544426 Å), equipped with an LYNXEYE XE-T detector. The diffractograms were collected within the 2θ range of 10–90° with a step size of 0.01° and scan rate of 0.375°/min.

Electrode Fabrication

The carbon paper working electrode (WE) served as the substrate for drop casting the catalyst ink, following pretreatment by ultrasonication in 3 M HCl, ultrapure water, and ethanol for 15, 10, and 5 min, respectively. It was then dried at 100 °C for 1 h to remove any contaminants and improve hydrophilicity. The catalyst ink was composed of 5 mg of the catalyst (either Pd or PdNi NPs), 5 mg of the Vulcan XC-72 carbon powder, 40 μL of 5% Nafion solution, 240 μL of isopropanol, and 720 μL of ultrapure water, resulting in a catalyst particle concentration of 5 mg mL–1. The catalyst ink was stirred overnight before being drop cast. The drop-casting process involved placing the carbon paper approximately 1.5 cm above a hot plate set at 60 °C. Subsequently, 50 μL of the catalyst ink was drop-cast onto one side of the carbon paper and allowed to dry for 10 min. After drying, the carbon paper was then flipped and an additional 50 μL of the catalyst ink was applied to the other side. After a 10 min drying period, the electrode was removed from the heat and left to dry in air overnight. In total, 0.5 mg of the catalysts were applied to the carbon paper, leading to a Pd mass of 0.5 mg for Pd/C and 0.299 mg of Pd and 0.201 mg of Ni for PdNi/C. The mass of Pd and Ni was determined by eqs S1 and S2, respectively.

Calculations of ECSA

A three-electrode cell (Figure S1) was used to calculate the Pd-based ECSA of Pd/C and PdNi/C by measuring the charge transferred by the reduction of a monolayer of PdO. In this setup, both anodic and cathodic chambers consisted of an N2-purged 1.0 M NaOH, Gly-free solution at 25 °C with a Nafion (212) membrane dividing the cell. The Nafion membrane was used to mitigate the crossover of GOPs from the anode chamber into the cathode chamber to prevent the possibility of the Pt cathode reducing the formed GOPs. Therefore, the ions passing through the Nafion membrane are most likely Na+ ions. The catalytic electrode served as the WE, a Pt grid served as the counter electrode (CE) in a 1 M NaOH solution, and the RE was Hg/HgO (1 M NaOH). It has been previously established that a monolayer of PdO is formed in 1 M NaOH at approximately 1.25 V vs RHE, (41) also corroborated in acidic conditions. (42,43) Hence, CV between 0.265 and 1.250 V vs RHE at a sweep rate of 50 mV s–1 was initially applied for 20 cycles under solution stirring to stabilize the catalysts.
Then, the solution was held stagnant, and two cyclic voltammograms were recorded within the same potential window and sweep rate. The second cycle was used for ECSA calculation by determining the associated charge of the PdO reduction peak and using eq 1
ECSA=Q(C)S(C/cm2)=areaofPdOreductionpeak405μC/cm2
(1)
where Q is the charge passed during the reduction of PdO to Pd, and S is the characteristic charge density (405 μC cm–2) of the reduction of a monolayer of PdO to Pd. (43)
The ECSA measurements are indicative of the catalysts that were used for the GEOR measurements. Hence, the normalization of the current shown for the Pd and PdNi NPs by the ECSA for the GEOR measurements was done with catalysts that had already been through cycling to the point where the current response was stable.

GEOR Electrochemical Measurements

All GEOR experiments were undertaken in a divided three-electrode cell (Figure S1), with the anode and cathode compartments separated by using a Nafion 212 membrane (VWR). The Pd/C and PdNi/C electrocatalysts were the WEs, a Pt grid was the CE, and the RE was Hg/HgO (1 M NaOH). The WE potential was converted to the reversible hydrogen electrode (RHE) scale using eq 2
ERHE=EHg/HgORef+EHg/HgOM+(0.0591×pH)
(2)
where ERHE is the calculated potential of the electrode in V vs RHE, EHg/HgORef is 0.120 V vs SHE at 25 °C (determined from laboratory measurement), EHg/HgOM is the measured or controlled potential during the experiments when using Hg/HgO (1 M NaOH), and the pH is 14 as the supporting electrolyte was 1 M NaOH. The respective solutions studied consisted of 0.10 and 0.50 M Gly in 1.0 M NaOH, purged with nitrogen before experiments. The electrochemical measurements were conducted at 25 and 40 °C, with a stirring bar at 200 rpm. The RE was kept at ambient temperature using a Luggin capillary. The activity of the catalysts for GEOR was mainly determined via ICPCs, which were conducted from low to high current densities. Steady-state galvanostatic measurements were used for GOP analysis.

Product Analysis by HPLC

HPLC analyses were performed with an Agilent 1260 Infinity II isocratic pump, multisampler, and multicolumn thermostat with a 1290 Infinity II refractive index detector. The analytical columns, in series, included a Bio-Rad guard column with a standard cartridge holder and a Micro-Guard cation H+ cartridge (4.6 × 30 mm), Bio-Rad Aminex HPX-87H column (7.8 × 300 mm), and Shodex SUGAR SH1011 column (8 × 300 mm). All columns were kept at 30 °C. To achieve optimal peak separation and ensure accurate results in the analysis of GOPs, two mobile phases were used: 1 mM H2SO4 and 8 mM H2SO4 at a flow rate of 0.25 mL min–1. The analysis time for each sample was 85 min. All standards for GOPs were calibrated from 0.1 to 10 mM with linear regression R2 values greater than 0.99. Samples were taken in 100 μL aliquots and diluted with 100 μL of ultrapure water. Chromatograms for each standard analyzed can be seen in Figures S2 and S3.

First-Principles Calculations

The slab models of the catalytic surfaces (Figure S4) were constructed using the atomic simulation environment (ASE). (44) The calculations were carried out on a (4 × 4 × 4) slab with a vacuum of 20 Å to avoid interactions between periodic images (Figure S4). The structures were optimized to energy and atom force convergence criteria of 10–5 eV and 0.01 eV·Å–1, respectively. Spin-polarized calculations were carried out, and the most stable spin state for all systems is reported in this work. DFT calculations were carried out using the Vienna Ab initio Simulation Package (VASP). (45) The exchange and correlation functional was approximated as the Bayesian error estimation functional, with an additional nonlocal correction term (BEEF-vdW). (46) Potential determining steps (PDSs) were determined following our previous studies. (47,48) As observed in Figures S5–S10, the GEOR was simulated considering three elementary pathways: (1) proton removal, (2) hydrolysis, and (3) hydrogen rearrangement. The DFT total energies were corrected using zero-point energies (ZPEs) and thermal contributions. The harmonic approximation was employed for the vibrational frequency calculations for all of the adsorbates and molecules. Henry’s law was used to link the gas-phase pressure to the aqueous concentration using the NIST-JANAF tables. (49) To account for the electrode/electrolyte interface, implicit water solvation was used as implemented in VASP. (50) The electrochemical environment was modeled based on a computational hydrogen electrode. (51) Further information regarding the computational methodology is provided in the Supporting Information.

Results and Discussion

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Characterization of the Nanoparticles

Figure 1a,c shows the TEM images and size distribution histograms of the well-defined Pd and PdNi NPs, respectively. The NPs were monodispersed with a mean particle diameter of 5.9 ± 0.7 nm for Pd and 2.98 ± 0.22 nm for PdNi. The Pd/Ni atomic ratio was nearly 1:1 (Pd0.45Ni0.55) as determined by TEM–EDS. HRTEM images of single Pd and PdNi NPs are shown in Figure 1b,d, respectively. The d-spacings measured from the lattice fringes, and averaged over 10 individual particles, were 0.227 and 0.225 nm for Pd and PdNi NPs, respectively, which is close to the lattice spacing for Pd(111) (0.223 nm) and agrees well with d111 ≈ 0.22 nm from the corresponding X-ray diffractograms (Figure 1e). The PXRD pattern of Pd NPs shows characteristic diffraction peaks that can be assigned to the (111), (200), (220), and (311) planes, which matched with face-centered cubic Pd (JCPDS 04-015-9339). The PXRD pattern of PdNi NPs exhibits the same features but with peaks widening due to a smaller particle size and a slight shift by ∼0.5° toward the higher 2θ values. The small peaks in the PXRD diffractogram of the PdNi alloy at 74, 76, and 78° are artifacts and not diffraction peaks.

Figure 1

Figure 1. TEM and HRTEM images of (a,b) Pd NPs and (c,d) PdNi NPs. The insets of images (a,b) show particle size distributions of the corresponding catalysts. (e) PXRD patterns of Pd and PdNi NPs.

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The crystallite sizes were estimated based on the (111) peaks using the Scherrer equation and were found to be 4.71 nm for Pd and 2.46 nm for PdNi NPs, which is slightly smaller than the TEM measurements indicating some polycrystallinity. (39) The characterization demonstrates that the synthesized Pd and PdNi NPs were predominantly composed of Pd(111) and PdNi(111) facets. Additionally, the lattice parameter of PdNi NPs, aPdNi = 3.88 Å, was smaller than that of Pd, aPd = 3.93 Å, indicating a lattice contraction due to successful alloying by incorporating Ni into the Pd lattice. (52−54)

Electrochemical Characterization

The ECSA of the Pd/C and PdNi/C catalysts was calculated through CV measurements in 1.0 M NaOH (Figure 2a). In the potential window of 0.5 to 1.0 V vs RHE, the cathodic peak is assigned to the reduction of PdO to Pd. The charge associated with this peak for Pd/C led to an ECSA of 68 ± 10 cm2, slightly more than double that of PdNi/C (29 ± 7 cm2). The total physical surface area for the PdNi NPs was estimated to be about 2.3 times larger than that of the Pd NPs by considering the mass loading, atomic composition, and morphology, assuming spherical NPs. Given these calculations, the ratio of the available Pd at the surface for Pd NPs to PdNi NPs should be approximately 1:1 using the atomic ratios determined by TEM–EDS. However, the ECSA of PdNi/C is less than half of that of Pd/C. There are two possible reasons that this might be the case.

Figure 2

Figure 2. (a) CV in 1.0 M NaOH for Pd/C and PdNi/C. (b) LSV in 1.0 M NaOH and 0.50 M Gly for Pd/C and PdNi/C along with the CV from (a). (c) LSV from (b) normalized by ECSA. (d) LSV from (b) normalized by the mass of Pd in the Pd/C and PdNi/C catalysts. All sweeps were conducted at 25 °C and a sweep rate of 50 mV s–1.

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The first is that the PdNi NPs may have a PdNi alloy composition gradient from the core to the surface with a more Pd-rich core and a more Ni-enriched surface. The second is that the smaller PdNi NPs have a higher packing density due to them being half the size of the Pd NPs, as it has been reported that the smaller the NPs, the higher the packing density. (55) This phenomenon for NPs has been widely reported in the literature. (56−58) However, the PdNi particles in the present study are very small (2.5–3.5 nm), and it is unlikely that there is much segregation in composition when comparing the center and rim of the particles. Additionally, the PXRD pattern for the PdNi alloy in Figure 1e also shows symmetric peaks without shoulders. Therefore, the Pd/Ni ratios determined through TEM–EDS are likely representative of the surface composition, and the decreased ECSA may be a result of the decreased physical surface area due to the packing density of the PdNi NPs. Additionally, based on our previous work on PdNi electrocatalysts for the GEOR, (16,33) the chemical state of Pd and Ni in the PdNi/C catalyst is likely to be elemental Pd and predominantly Ni(OH)2, respectively.
To ascertain the electrochemical response of the GEOR for Pd/C and PdNi/C, linear sweep voltammetry (LSV) was recorded in 1.0 M NaOH and 0.50 M Gly (Figure 2b). The addition of Gly resulted in a significant increase in the anodic current, i.e., the GEOR, with an onset potential of approximately 0.6 V vs RHE for both catalysts. Although the LSV for Pd/C in Figure 2b reaches a higher current (mA) than PdNi/C at the most positive potential, when normalized by the ECSA of the active Pd sites and the mass of Pd in the catalysts, the PdNi/C has higher performance (specific activity: Pd/C = 1.3 mA cm–2; PdNi/C = 2.2 mA cm–2, mass activity: Pd/C = 170 mA mgPd–1; PdNi/C = 211 mA mgPd–1). These comparisons can be seen in Figure 2c,d for specific activity and mass activity, respectively. However, given the notable iR-drop observed in the LSV, the performance of both electrocatalysts was comparatively evaluated through ICPCs.
To determine the most suitable anolyte for the GEOR, ICPCs for PdNi/C were recorded using two different Gly concentrations, 0.10 and 0.50 M, in a supporting electrolyte of 1.0 M NaOH, see Figure 3. The ICPCs showed a similar trend; as the current is increased, the corresponding potential also increases up until a specific current level is reached, at which point it sharply spikes. This spike represents the deactivation of the catalyst for the GEOR, which occurs due to the oxidation of the active Pd sites. (16,59) The current and corresponding potentials preceding this spike are denoted as the critical current icr (or critical current density jcrECSA for specific activity, or critical current when normalized by mass jcrmass for mass activity) and the critical potential Ecr, respectively. For 0.50 M Gly solution, the icr, jcrECSA, and jcrmass are all approximately double compared to 0.10 M Gly, demonstrating that the higher Gly concentration results in enhanced overall performance for the GEOR. However, despite the fivefold increase in Gly concentration, this did not translate into a fivefold increase in activity. Notably, the PdNi/C catalyst also reached a higher Ecr in the solution with a higher Gly concentration, indicating that catalyst deactivation occurred at a higher potential. Since the 0.50 M Gly solution resulted in icr, jcrECSA, jcrmass, and Ecr values higher than those of the 0.10 M solution, the former was chosen to compare the performance of Pd/C and PdNi/C at 40 °C.

Figure 3

Figure 3. ICPCs for PdNi/C at 40 °C in a supporting electrolyte of 1.0 M NaOH with Gly concentrations of 0.10 M (blue triangles) and 0.50 M (red circles). (a) No normalization, i.e., current; (b) specific activity, i.e., normalized by ECSA; and (c) mass activity, i.e., normalized by the mass of Pd in the PdNi/C catalyst.

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The comparative ICPCs presented in Figure 4a reveal that the Pd/C catalyst achieves a higher icr of 199 mA compared to PdNi/C, which exhibits a icr of 159 mA. This higher icr is expected since Pd/C has a higher mass of Pd and a larger ECSA than PdNi/C, so the overall current is naturally higher, considering that the GEOR occurs on Pd sites. However, when the data are normalized by ECSA in Figure 4b, PdNi/C emerges as the superior catalyst by active sites for the GEOR. PdNi/C reaches a jcrECSA of 4.4 mA cm–2 compared to that of 2.8 mA cm–2 for Pd/C. This represents a 57% increase in specific activity by the PdNi/C catalyst. The significant increase in specific activity for PdNi/C was not equivalently repeated in terms of mass activity. However, the mass activity of PdNi/C shown in Figure 4c reaches a jcrmass of 531 mA mgPd–1 which is 34% higher than that of Pd/C at 397 mA mgPd–1. Given that the active surface of PdNi/C contains a smaller portion of available Pd than Pd/C, as discussed earlier, these results show that PdNi/C is inherently a more active catalyst for the GEOR, clearly demonstrating the positive role of Ni, at an approximate 1:1 Pd/Ni ratio. Furthermore, since the cost of Pd, at the time of writing, is nearly 2000 times higher than Ni, (60,61) by substituting approximately 40% of Pd, by mass, with Ni in the form of PdNi, a higher jcrmass can be reached at around two-thirds of the cost. Hence, the addition of Ni to Pd NPs enables a superior catalyst at a lower price. In Figure 4a–c, the Ecr is consistently higher for PdNi/C than for Pd/C in all three cases, indicating that Pd/C deactivates more readily at a potential lower than that of PdNi/C. This further emphasizes the advantage and superiority of the PdNi/C catalyst.

Figure 4

Figure 4. ICPCs for Pd/C (black squares) and PdNi/C (red circles) at 40 °C in a 1.0 M NaOH and 0.50 M Gly solution. (a) No normalization, i.e., current; (b) specific activity, i.e., normalized by ECSA; and (c) mass activity, i.e., normalized by the mass of Pd in the Pd/C and PdNi/C catalysts.

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Since it is well known that for the GEOR, Ni oxidizes Gly at significantly higher potentials than Pd, the Ni present in the PdNi/C catalyst is likely only aiding in the activity of the Pd sites for the GEOR. Indeed, significant work has been done to show that the GEOR on Ni occurs as a result of the oxidation state change in Ni from Ni2+ to Ni3+ in the forms of Ni(OH)2 and NiOOH, respectively. (62) The oxidation state change occurs around 1.4 V vs RHE, and therefore studies on Ni for the GEOR regularly show the onset potential being around the mentioned voltage. Hence, the GEOR onset potential for Ni compared to Pd is around 700 mV higher. (16) Additionally, an increased onset potential and utilization of monometallic catalysts such as non-noble transition metals like Ni reportedly result in a significant C–C cleavage in highly alkaline conditions and, consequently, decreased yields of highly valued C3 GOPs are reported. (63) This is not the case from the HPLC GOP analysis presented in this study (vide infra).
The reason for the superior performance when noble metals are combined with non-noble metals is a topic of debate in the literature. The two main themes are the bifunctional mechanism and electronic effect. For the bifunctional mechanism, the addition of an oxophilic metal such as Ni to a noble metal catalyst enhances the catalytic activity by providing an increased amount of proximal hydroxide species adjacent to the GEOR active sites. (11,15,64) The enhanced activity is then a result of either the increased hydroxide species providing a more oxidative environment, participating in the GEOR or aiding the oxidative removal of inhibiting COad intermediates. For the electronic effect, the addition of non-noble transition metals to the lattice of noble metals such as Pt and Pd decreases the binding energy for inhibiting species such as CO (27) and OH, (65) and it can increase the number of available surface electrons (66) and lower glycerol adsorption energy; (66) the result being easier desorption of intermediates and, therefore, increased active sites during the GEOR as well as less C–C bond cleavage. From the perspective of this study, it is difficult to discern definitively which process explains the increased performance of PdNi/C over Pd/C, but both processes seem plausible. However, the study conducted on PtNi by Luo et al. (65) provides a detailed body of evidence pertaining to the role of Ni in enhancing the catalytic activity of Pt being a result of the electronic effect.
Note that in the present study, we have avoided kinetic analyses from the Tafel slope as calculating Tafel slopes from the ICPCs for the GEOR is problematic, as the reaction mechanism may vary along the polarization curve. Hence, the calculation of such slopes may be misleading and may not give true indications of a single reaction-limiting step.

Glycerol Oxidation Product Analysis

To analyze the GOPs generated by the PdNi/C and Pd/C catalysts, galvanostatic measurements were conducted in 0.50 M Gly in 1.0 M NaOH solutions to a final charge of 18C (Figures S11 and S12). Although long-term stability is an important aspect of electrocatalytic systems, the goal of this study was to synthesize the (111) crystal facet catalysts and directly compare their activity and product distribution experimentally and computationally close to the GEOR onset potential. That is why, for the experimental determination of the GOPs, a small volume of solution was used, and only 18C were passed such that a readable concentration of products could be determined in a short period of time. Further work on these catalysts in a larger volume cell setup, in which the catalysts can be used for extended periods to assess the stability, is important to be pursued. However, given that the NPs are somewhat spherical, it would be challenging to detect changes to the morphology or structure of such small particles (6 nm for Pd and 3 nm for PdNi).
The product analysis resulting from the galvanostatic measurements is presented as product fractions of the sum of the overall GOP concentrations in Table 1 and Figure 5 as a function of measured potential. A result of the experiments being performed galvanostatically is that the average potential during the experiments slightly differs between runs. Therefore, the measured potential for each experiment was corrected for the iR-drop in the electrochemical cell, and then the average potential, in addition to the standard deviation (SD), was calculated over the entire run. For repeat experiments, the same process was adopted, then a second average and SD were determined for the combined number of experiments. The average and SD of the WE potential are reported in Table 1, which shows that the potentials for the comparison of PdNi/C to Pd/C are not exactly the same but are within the SD. The potentials analyzed were chosen to be close to the GEOR onset because the catalysts become less selective, and C–C bond cleavage is more likely at higher potentials. The GOP concentrations determined by HPLC analysis were normalized by the charge passed and then converted to a fraction.
Table 1. Product Fractions of GOPs and Glycerol Conversion from Galvanostatic Experiments Using Pd/C and PdNi/C in 0.50 M Gly and 1.0 M NaOHa
electrocatalyst, V vs RHEproduct fraction average ± standard deviation (%)Gly conversion (%)
(number of experiments)GLALATTAFAGAOAAA 
PdNi/C, 0.983 ± 0.003 V (1)56273.89.90.92.302.4
PdNi/C, 0.846 ± 0.021 V (3)58 ± 429 ± 25.3 ± 0.61.1 ± 1.22.2 ± 1.73.6 ± 0.60.6 ± 0.41.4 ± 0.5
PdNi/C, 0.721 ± 0.015 V (2)60 ± 130 ± 16.6 ± 0.10.5 ± 0.50 ± 02.1 ± 0.40.6 ± 0.61.3 ± 0.6
PdNi/C, 0.688 ± 0.029 V (2)61 ± 430 ± 45.5 ± 2.01.8 ± 1.80 ± 01.2 ± 0.50.5 ± 0.51.6 ± 0.0
Pd/C, 0.832 ± 0.049 V (2)60 ± 024 ± 05.9 ± 0.15.6 ± 1.02.1 ± 2.11.8 ± 0.41.0 ± 1.01.6 ± 0.1
Pd/C, 0.734 ± 0.020 V (3)62 ± 226 ± 26.3 ± 0.52.0 ± 1.51.4 ± 0.61.4 ± 0.81.6 ± 1.21.9 ± 0.2
Pd/C, 0.672 ± 0.022 V (4)64 ± 224 ± 38.3 ± 1.30.6 ± 0.50.5 ± 0.42.8 ± 0.90.5 ± 0.42.3 ± 0.4
a

18C passed for each measurement.

Figure 5

Figure 5. Product fractions analyzed by HPLC for (a) PdNi/C and (b) Pd/C catalysts at varying potentials.

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The product fractions listed in Table 1 show that an increased potential for both PdNi/C and Pd/C results in lower product fractions for GLA and LA. Overall, the two main products, GLA and LA, are formed in similar proportions as a function of potential for both PdNi/C and Pd/C. Additionally, to demonstrate C–C cleavage at higher potentials, one experiment was done at 0.983 V vs RHE for PdNi/C leading to a larger product fraction of FA. Figure 5 graphically illustrates the data presented in Table 1 and shows that, remarkably, there is very little difference in the product fraction distribution of the GOPs for Pd/C and PdNi/C with there being a maximum of 3 and 5% differences between the product fractions for GLA and LA, respectively, observed at similar potentials. The Gly conversion % shown in Table 1 is quite low due to the high concentration of Gly in solution and relatively short electrolysis times evaluated, which were done to minimize the chemical reactions that can occur in alkaline solution.
Figure 5 shows a decrease in the selectivity for GLA as the potential increases, for both PdNi/C and Pd/C. At the lowest examined potentials of 0.688 V vs RHE for PdNi/C and 0.672 V vs RHE for Pd/C, the product selectivity to GLA was the highest, with product fractions of 64 and 61%, respectively. This suggests that the closer the anodic potentials are to the GEOR onset potential and likewise to the PDS potential calculated by DFT (vide infra), the higher the selectivity toward the formation of GLA. At higher potentials, comparing PdNi/C and Pd/C at 0.721 V vs RHE and 0.734 V vs RHE, respectively, the GLA product fraction was 60 and 62% for PdNi/C and Pd/C, respectively. Therefore, under the current experimental conditions, the reaction pathway is not significantly altered by the addition of Ni to Pd. Hence, the PdNi/C demonstrates improved electrochemical performance for the GEOR compared to Pd/C, as discussed earlier, without compromising the selectivity for the predominant GLA product.
The second most abundant product was LA. Figure 5 demonstrates that PdNi/C had a slightly higher selectivity to lactate than Pd/C. However, the overall similar product fractions for the two catalysts further illustrate that the reaction pathways are not significantly altered by alloying Ni with Pd. At the highest potential studied for PdNi/C, 0.983 V vs RHE, the product fractions for GLA and LA were the lowest, and there was an increased selectivity to FA compared to lower potentials. This decrease in selectivity for C3 GOPs at higher potentials has also been reported previously. (67,68) The same increase in the FA product fraction at a higher potential also occurred for Pd/C at 0.832 V vs RHE when compared to lower potentials. Interestingly, there was a lower FA product fraction for PdNi/C at 0.846 V vs RHE than for Pd/C at 0.832 V vs RHE, suggesting a lower affinity for C–C bond cleavage.
In comparison to the present study, reports on Pt (69) and PtNi (65,70) in alkaline media have shown varied results as to the main product generated during the GEOR. On a Pt RDE, Melle et al. (69) showed that for supporting electrolytes of LiOH, NaOH, and KOH, LA and GLA are generated in approximately even amounts close to the GEOR onset potential, but for NaOH, LA formation dominates at higher potentials. For PtNi, Luo et al. (65) reported that close to the onset potential for the GEOR (0.5 V vs RHE), Pt/C and Pt1.2Ni1 supported on carbon paper (ratio of Pt/Ni in at. %) had similar selectivity with approximately 40% of the products assigned to GLA and the remaining 60% being TTA. The authors noted that only low quantities of LA were formed. Furthermore, at a higher potential (0.7 V vs RHE), the selectivity toward GLA dropped considerably for both Pt/C and Pt1.2Ni1 to around 20%, whereas in the present study, an increase of around 200 mV from the lowest studied potential shows no such decline in the product fraction of GLA. In contrast to Luo et al., (65) for Pt and Pt67Ni33 supported by graphene nanosheets under an applied potential close to the GEOR onset, Zhou et al. (70) reported GA to be the dominant product in both cases with around 40% selectivity. Additionally, the authors found GD and GLA present in both cases but with Pt having higher selectivity toward GD and Pt67Ni33 favoring GLA, whereas in the present study with PdNi, GD was not detected, and GA was a minor product.
In summary, the general trends from the product analysis indicate that PdNi/C maintains the selectivity for GLA and exhibits slightly higher selectivity for LA when compared to Pd/C. The selectivity toward GLA decreases only slightly at higher potentials for both Pd/C and PdNi/C. Despite the increased specific activity for the PdNi/C catalyst compared to Pd/C, it is remarkable that the product selectivity is consistently maintained at various potentials. The similar GEOR pathways for the two catalysts were confirmed through DFT calculations.

Density Functional Theory Calculations

Figure 6 shows the computed PDS for GEOR to form common liquid products. All reactions are labeled from 1 to 6. The oxidation of the secondary hydroxyl group on Gly can undergo either pathway 1, forming dihydroxyacetone (DHA) or hydroxypyruvic acid (HPA) as the major product (Gly–DHA–HPA); or pathway 6, forming DHA or LA as the major product (Gly–DHA–LA). The oxidation of the primary hydroxyl group on Gly follows pathway 2, forming glyceraldehyde (GD) or GLA as the major oxidation product (Gly–GD–GLA).

Figure 6

Figure 6. Representation of the calculated Gly electrooxidation pathway of Pd(111) and PdNi(111) catalysts in alkaline solution with PDS values (in eV) of each oxidation step. The oxidation pathway of each intermediate is shown using different colors as follows: (1) Gly–DHA (black), (1′) DHA–HPA (black), (2) Gly–GD (blue), (2′) GD–GLA (blue), (3) GLA–GA (red), (3′) GA–FA (red), (4) GLA–TTA (magenta), (4′) TTA–MLA (magenta), (5) GA–OA (gray), and (6) DHA–LA (green). Here, PDS represents the minimum potential required to overcome the energy barrier of the reactions illustrated in Figures S5–S10.

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The Pd and PdNi surfaces require smaller PDS values (Pd: 0.66 eV, PdNi: 0.39 eV) in pathway 1 to form GLA and pathway 6 to form LA (Pd: 0.58 eV, PdNi: 0.36 eV) than following pathway 2 to form HPA (Pd: 0.66 eV, PdNi: 0.39 eV). Table 2 summarizes the PDS required to form the GOPs starting from the Gly molecule. The PDSs of GLA and LA are the lowest values, which justifies the higher product fraction of both species obtained by HPLC. For a close-packed Pd structure (Pd(111)), Valter et al. (71,72) found, using DFT calculations, that the first deprotonation step leading to the adsorption of Gly to Pd favors adsorption by the secondary carbon and that after two deprotonation steps, Gly was bound by both primary and secondary carbon. The authors noted that while this form of adsorption should give either GD or DHA, in experimental studies, the GD pathway was more commonly reported with the subsequent oxidation step, in alkaline conditions, forming GLA. Additionally, the authors found that the first adsorption/deprotonation step for Pt(111) mirrored that of Pd(111) but that the second adsorption step likely favored both primary carbons bound to Pt. This may be a reason for the difference in the product distribution observed in the present study compared to that of Pt and PtNi studies in alkaline media discussed earlier.
Table 2. Calculated PDS Values to Obtain the Liquid Products Are Given in Figure 6a
productsreactionCiPdPdNi
glycerateGly–GD–GLAC30.690.39
lactateGly–DHA–LAC30.580.36
tartronateGly–GD–GLA–TTAC30.660.46
formateGly–GD–GLA–GA–FAC10.690.46
glycolateGly–GD–GLA–GAC20.690.38
oxalateGly–GD–GLA–GA–OAC20.680.41
a

All PDS values are in eV.

The experimental product fraction of LA was considerably lower than that of GLA, which can be explained by two main reasons: (i) LA formation involves a series of chemical steps including C–O cleavage (Figure S10), which are not affected by the applied potential and (ii) the interconversion of GD and DHA leads to the LA route as the minor pathway. For (ii), DHA is unstable under alkaline conditions and can be converted into GD or pyruvaldehyde (PV), resulting in either GLA or LA formation, respectively. These conversions are more likely than HPA formation from DHA since the PDS for HPA formation is higher, (73−75) as shown in Figure 6 for reaction (1′). Although the formation of LA from PV is a known reaction, (76) and the DFT calculations show that PV and LA formation from DHA has a common intermediate (Figure S13), the formation of GD from DHA has been shown to have a higher rate constant than PV formation at elevated temperatures in alkaline conditions. (77) Therefore, it is likely that there is a mix of LA, PV, and GD chemically produced after any electrochemical DHA formation but with a preference for the interconversion of DHA to GD. Hence, GLA formation can be achieved electrochemically from GD in greater proportions than the chemical formation of LA mentioned in (i).
Table 2 presents data showing that, for all of the GOPs experimentally detected, PdNi has a lower PDS than Pd. This observation aligns with the experimental findings, indicating that PdNi/C catalysts exhibit superior electrocatalytic activity compared to Pd/C while maintaining selectivity toward valuable GOPs, such as GLA and LA.

Conclusions

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The addition of Ni to Pd to create PdNi NPs has proven to be an effective strategy for improving the performance of the GEOR under alkaline conditions. The novelty of the present study involves the successfully tuned synthesis of pure Pd and alloyed Pd0.45Ni0.55 (at. %) NPs, which are very close to the desired pure Pd(111) and PdNi(111) and resulted in nanocatalysts of a certain morphology and composition that were further investigated as promising materials for the GEOR supported by the DFT modeling. Catalyst fabrication procedures usually focus on the composition or morphology; meanwhile, we attempted to fix both aspects. PdNi/C exhibited significantly enhanced specific and mass activity compared to Pd/C, as analyzed by ICPCs. Generally, reports in the literature will show either specific activity or mass activity, but in our study, PdNi was the superior catalyst in both cases. Additionally, PdNi/C was able to operate at potentials higher than those of Pd/C before deactivation by PdO formation. The DFT calculations for the formation of all experimentally detected GOPs consistently indicated lower PDS values for PdNi than Pd, thereby supporting the electrochemical findings. Both PdNi/C and Pd/C displayed high selectivity toward GLA and LA, with product fractions of around 60 and 30%, respectively. At increased potentials, the selectivity for GLA and LA decreased but remained above 50 and 20%, respectively, with PdNi/C exhibiting slightly higher selectivity for LA than Pd/C. This study combines experimental and computational approaches to unambiguously establish that bimetallic PdNi NPs are promising electrocatalysts for the GEOR, significantly improving the activity compared to monometallic Pd while maintaining the selectivity for valuable GOPs. The number of studies including the quantitative analysis of GOPs using HPLC for PdNi catalysts, especially coupled with DFT calculations, is limited in the literature; hence, the findings of the present study provide new insights for the field.

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsaem.3c02789.

  • Experimental methods used for the electrochemical measurements, HPLC standards, description of computational details, and experimental results of galvanostatic measurements (PDF)

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Author Information

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  • Corresponding Authors
  • Authors
    • Irina Terekhina - Department of Materials and Environmental Chemistry, Stockholm University, Stockholm SE-10691, Sweden;  Orcidhttps://orcid.org/0000-0002-4759-5895
    • Daniel Martín-Yerga - Department of Chemistry, Nanoscience Center, University of Jyväskylä, Jyväskylä FI-40014, Finland;  Orcidhttps://orcid.org/0000-0002-9385-7577
    • Lars G. M. Pettersson - FYSIKUM, AlbaNova University Center, Stockholm University, Stockholm SE-106 91, Sweden
    • Mats Johnsson - Department of Materials and Environmental Chemistry, Stockholm University, Stockholm SE-10691, Sweden;  Orcidhttps://orcid.org/0000-0003-4319-1540
    • Ann Cornell - Department of Chemical Engineering, KTH Royal Institute of Technology, Stockholm SE-100 44, Sweden;  Orcidhttps://orcid.org/0000-0001-5816-2924
  • Author Contributions

    J.W., I.T., and E.C.d.S. contributed equally. The manuscript was written through contributions from all authors. All authors have given approval to the final version of the manuscript.

  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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The authors would like to acknowledge the Swedish Foundation for Strategic Research for funding this work through grant no. EM16-0010. The computations were enabled by resources provided by the National Academic Infrastructure for Supercomputing in Sweden (NAISS) and the Swedish National Infrastructure for Computing (SNIC) at the PDC and NSC centers partially funded by the Swedish Research Council through grant agreement nos. 2022-06725 and 2018-05973. D.M.-Y. thanks the Research Council of Finland for financial support (ref. 355569). The authors acknowledge that portions of this manuscript included the Ph.D. thesis written by J.W., entitled From Facets to Flow: The Electrooxidation of Glycerol on Pd-based catalysts (2023), for which J.W. holds the copyright (ISBN: 978-91-8040-752-6).

Abbreviations

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CV

cyclic voltammetry

DFT

density functional theory

DHA

dihydroxyacetone

ECSA

electrochemical surface area

FA

formic acid/formate

GA

glycolic acid/glycolate

GD

glyceraldehyde

GEOR

glycerol electrooxidation reaction

GLA

glyceric acid/glycerate

Gly

glycerol

GOPs

glycerol oxidation products

HPA

hydroxypyruvic acid

ICPCs

iR-corrected polarization curves

LA

lactic acid

MLA

mesoxalic acid

NPs

nanoparticles

OA

oxalic acid/oxalate

PDS

potential determining step

PXRD

powder X-ray diffraction

RHE

reversible hydrogen electrode

TEM

transmission electron microscopy

TTA

tartronic acid/tartronate

References

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    A review. Electrosynthesis, a historically powerful tool for the prodn. of a no. of industrial-scale inorg. or org. materials, has experienced a renaissance over the last 10 years with research efforts seeking a dual prodn. platform for mols. and energy carriers. It is termed a Power-to-X approach. Specifically, H (H2) is a key compd. in emerging energy conversion and storage systems, acting as an energy carrier to provide elec. energy with a significantly reduced environmental footprint through H2/O2 fuel cells. The clean energy prodn. strategy from energy carriers is inversely termed an X-to-Power approach. However, H2 sources remain up to now the main key challenge. Increasing interest surrounds the development of advanced low energy consumption electrolysis cells enabling reliable, sustainable and dual prodn. of both H2 and valuable chems. from the selective oxidn. of surplus biomass-derivs. It can thus be summed up that the tremendous idea of generating electricity or producing fuels such as H2 while synthesizing chems. is an attractive pathway for org. synthesis and electricity prodn. However, precisely how this could be achieved in a cheap and sustainable way remains a puzzle for scientists. However, orgs. selective electrooxidn. reactions are central topics and bridge fuel cell and electrolysis cell research. A no. of (bio)catalytic interfaces have been developed to overcome their sluggish electrochem. kinetics. Within this perspective, the authors propose a detailed review on the recent advances over the last 10 years in co-generative fuel cells and electrolysis cells that operate with biomass-based org. mols. (EtOH, ethylene glycol, glycerol, (oligo)saccharides, cellulose, hemicellulose) while highlighting exptl. and theor. research that unifies those fields to yield devices with improved performance. The identified main electrocatalytic reaction descriptors allow for new materials to be proposed, which could enable maximized activity, selectivity and durability of anode materials. This perspective particularly enlightens the missing fundamental knowledge on parameters dictating electrocatalysis of org. compds. in aq. media. Overall, the implications for the wider scientific community of electrochem., electrocatalysis, materials science and org. chem., and finally provide several logical pathways and guidelines to stimulate progress, inspiring the development of org.-fuelled cogeneration electrochem. devices are discussed.
  9. 9
    Wu, J.; Yang, X.; Gong, M. Recent Advances in Glycerol Valorization via Electrooxidation: Catalyst, Mechanism and Device. Chin. J. Catal. 2022, 43 (12), 2966– 2986,  DOI: 10.1016/S1872-2067(22)64121-4
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    Recent advances in glycerol valorization via electrooxidation: Catalyst, mechanism and device
    Wu, Jianxiang; Yang, Xuejing; Gong, Ming
    Chinese Journal of Catalysis (2022), 43 (12), 2966-2986CODEN: CJCHCI; ISSN:1872-2067. (Elsevier B.V.)
    A review. Glycerol is one of the most important biomass-based platform mols., massively produced as a byproduct in the biodiesel industry. Its high purifn. cost from the crude glycerol raw material limits its application and demands new strategies for valorization. Compared to the conventional thermocatalytic strategies, the electrocatalytic strategies can not only enable the selective conversion at mild conditions but also pair up the cathodic reactions for the co-prodn. with higher efficiencies. In this review, we summarize the recent advances of catalyst designs and mechanistic understandings for the electrocatalytic glycerol oxidn. (GOR), and aim to provide an overview of the GOR process and the intrinsic structural-activity correlation for inspiring future work in this field. The review is dissected into three sections. We will first introduce the recent efforts of designing more efficient and selective catalysts for GOR, especial toward the prodn. of value-added products. Then, we will summarize the current understandings about the reaction network based on the ex-situ and in-situ spectroscopic studies as well as the theor. works. Lastly, we will select some representative examples of creating real electrochem. devices for the valorization of glycerol. By summarizing these previous efforts, we will provide our vision of future directions in the field of GOR toward real applications.
  10. 10
    Ge, R.; Li, J.; Duan, H. Recent Advances in Non-Noble Electrocatalysts for Oxidative Valorization of Biomass Derivatives. Sci. China Mater. 2022, 65 (12), 3273– 3301,  DOI: 10.1007/s40843-022-2076-y
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    10
    Recent advances in non-noble electrocatalysts for oxidative valorization of biomass derivatives
    Ge, Ruixiang; Li, Jing; Duan, Haohong
    Science China Materials (2022), 65 (12), 3273-3301CODEN: SCMCDB; ISSN:2095-8226. (Science China Press)
    A review. Electrocatalysis is deemed as a promising approach for sustainable energy conversion and chem. prodn. Although a variety of cathode reactions (e.g., hydrogen evolution and CO2/N2 redn.) produce valuable fuels and chems., the extensively studied oxygen evolution reaction (OER) at anode only generates O2, which is not a high-value product. Substituting the OER with thermodynamically more favorable biomass deriv. oxidn. reactions (BDORs) not only enables energy-saving electrocatalysis, but also provides value-added anode products. Recent achievements have demonstrated that non-noble electrocatalysts are promising for BDORs. Herein, we provide a comprehensive review on recent achievements in the field of electrochem. BDORs catalyzed by non-noble catalysts. We start by summarizing the electrocatalytic oxidn. of different types of biomass-derived substrates, aiming to show the advantages of the electrocatalytic pathway and to introduce the state-of-the-art non-noble catalysts. The reaction mechanisms of non-noble-material-catalyzed BDORs are then summarized and classified into three types according to the acceptor of hydrogen species during the dehydrogenation of biomass derivs. Subsequently, discussions are devoted to the strategies for promoting the performances of non-noble electrocatalysts. Finally, we propose our opinions regarding future trends and major challenges in this field.
  11. 11
    Simões, M.; Baranton, S.; Coutanceau, C. Electro-Oxidation of Glycerol at Pd Based Nano-Catalysts for an Application in Alkaline Fuel Cells for Chemicals and Energy Cogeneration. Appl. Catal., B 2010, 93 (3–4), 354– 362,  DOI: 10.1016/j.apcatb.2009.10.008
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    11
    Electro-oxidation of glycerol at Pd based nano-catalysts for an application in alkaline fuel cells for chemicals and energy cogeneration
    Simoes, Mario; Baranton, Steve; Coutanceau, Christophe
    Applied Catalysis, B: Environmental (2010), 93 (3-4), 354-362CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
    C-supported Pd, Pt, Au and bimetallic PdAu and PdNi nano-catalysts with different compns. were synthesized. Their catalytic activity toward glycerol electrooxidn. was evaluated in alk. medium. Phys. and electrochem. methods where used to characterize the structure and the surface of the catalysts. The PdxAu1-x/C catalysts were alloys, which present an increase of crystallite (XRD) and particle (TEM) sizes with increasing Au at. fraction. Their surfaces were Pd rich whatever the Pd at. ratio. The structure of the Pd0.5Ni0.5/C catalyst is much more difficult to understand, but it seems to be composed of a Pd phase in interaction with a Ni(OH)2 phase. The onset potential of glycerol oxidn. is ∼0.15 V lower on Pt/C than on Pd/C and Au/C. All PdxMe1-x/C catalysts presented a lower onset potential than monometallic Au/C and Pd/C ones, but higher than Pt/C. For bimetallic catalysts, the order of activity at low potentials is: Pd0.3Au0.7/C > Pd0.5Au0.5/C > Pd0.5Ni0.5/C. Electrochem. expts. and in situ IR spectroscopy showed that glycerol electrooxidn. mechanism is dependent on the catalyst, leading to different reaction products. Adsorbed CO species are detected on monometallic Pt and on Pd-rich catalysts, but not on Au and Pd0.3Au0.7 catalysts, indicating that they cannot break the C-C bond. The formation of hydroxypyruvate ion, which is a costly chem. product, is detected on pure Au catalyst.
  12. 12
    Chen, X.; Granda-Marulanda, L. P.; McCrum, I. T.; Koper, M. T. M. How Palladium Inhibits CO Poisoning during Electrocatalytic Formic Acid Oxidation and Carbon Dioxide Reduction. Nat. Commun. 2022, 13 (1), 38,  DOI: 10.1038/s41467-021-27793-5
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    How palladium inhibits CO poisoning during electrocatalytic formic acid oxidation and carbon dioxide reduction
    Chen, Xiaoting; Granda-Marulanda, Laura P.; McCrum, Ian T.; Koper, Marc T. M.
    Nature Communications (2022), 13 (1), 38CODEN: NCAOBW; ISSN:2041-1723. (Nature Portfolio)
    Development of reversible and stable catalysts for the electrochem. redn. of CO2 is of great interest. Here, we elucidate the atomistic details of how a palladium electrocatalyst inhibits CO poisoning during both formic acid oxidn. to carbon dioxide and carbon dioxide redn. to formic acid. We compare results obtained with a platinum single-crystal electrode modified with and without a single monolayer of palladium. We combine (high-scan-rate) cyclic voltammetry with d. functional theory to explain the absence of CO poisoning on the palladium-modified electrode. We show how the high formate coverage on the palladium-modified electrode protects the surface from poisoning during formic acid oxidn., and how the adsorption of CO precursor dictates the delayed poisoning during CO2 redn. The nature of the hydrogen adsorbed on the palladium-modified electrode is considerably different from platinum, supporting a model to explain the reversibility of this reaction. Our results help in designing catalysts for which CO poisoning needs to be avoided.
  13. 13
    Oliveira, V. L.; Morais, C.; Servat, K.; Napporn, T. W.; Tremiliosi-Filho, G.; Kokoh, K. B. Glycerol Oxidation on Nickel Based Nanocatalysts in Alkaline Medium - Identification of the Reaction Products. J. Electroanal. Chem. 2013, 703, 56– 62,  DOI: 10.1016/j.jelechem.2013.05.021
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    Glycerol oxidation on nickel based nanocatalysts in alkaline medium - Identification of the reaction products
    Oliveira, V. L.; Morais, C.; Servat, K.; Napporn, T. W.; Tremiliosi-Filho, G.; Kokoh, K. B.
    Journal of Electroanalytical Chemistry (2013), 703 (), 56-62CODEN: JECHES; ISSN:1873-2569. (Elsevier B.V.)
    Carbon-supported Ni-based nanoparticles were prepd. by the impregnation method and used as anode electrocatalysts for glycerol conversion. These metallic powders were mixed with a suitable amt. of a Nafion/water soln. to make catalytic inks which were then deposited onto the surface of C Toray used as a conductive substrate. Long-term electrolyzes of glycerol were carried out in alk. medium by chronoamperometry expts. Anal. of the oxidn. products was performed with ion-exclusion liq. chromatog. which separates the analytes by ascending pKa. The spectroscopic measurements showed that the Co content in the anode compn. did contribute to the CC bond cleavage of the initial mol. of glycerol.
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    Holade, Y.; Morais, C.; Arrii-Clacens, S.; Servat, K.; Napporn, T. W.; Kokoh, K. B. New Preparation of PdNi/C and PdAg/C Nanocatalysts for Glycerol Electrooxidation in Alkaline Medium. Electrocatalysis 2013, 4 (3), 167– 178,  DOI: 10.1007/s12678-013-0138-1
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    14
    New Preparation of PdNi/C and PdAg/C Nanocatalysts for Glycerol Electrooxidation in Alkaline Medium
    Holade, Yaovi; Morais, Claudia; Arrii-Clacens, S.; Servat, K.; Napporn, T. W.; Kokoh, K. B.
    Electrocatalysis (2013), 4 (3), 167-178CODEN: ELECCF; ISSN:1868-2529. (Springer)
    PdAg/C and PdNi/C nanomaterials with different at. compns. were successfully synthesized by a "bromide anion exchange" method and applied to the glycerol electrooxidn. in alk. medium. The catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), differential and thermogravimetric anal., electrochem. cyclic voltammetry, CO stripping, and spectroelectrochem. XRD showed a small crystallite size between 3 and 4 nm for PdNi/C, and 3 and 6 nm for PdAg/C. TEM results showed a good dispersion of the particles on the carbon support and a particle mean size ranging from 3.73 to 3.97 nm. The electrochem. expts. have highlighted a high specific electrochem. surface area for the different catalysts such as 69.20 m2 g-1 for Pd/C. Furthermore, all the bimetallic catalysts exhibited a good kinetic towards glycerol electrooxidn. when compared to the monometallic material Pd/C and at lower potential values. The Pd60Ni40/C catalyst is outstandingly active, being therefore a good candidate for electrochem. valorization of glycerol conversion.
  15. 15
    Holade, Y.; Morais, C.; Servat, K.; Napporn, T. W.; Kokoh, K. B. Toward the Electrochemical Valorization of Glycerol: Fourier Transform Infrared Spectroscopic and Chromatographic Studies. ACS Catal. 2013, 3 (10), 2403– 2411,  DOI: 10.1021/cs400559d
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    Toward the Electrochemical Valorization of Glycerol: Fourier Transform Infrared Spectroscopic and Chromatographic Studies
    Holade, Yaovi; Morais, Claudia; Servat, Karine; Napporn, Teko W.; Kokoh, K. Boniface
    ACS Catalysis (2013), 3 (10), 2403-2411CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
    Glycerol electrooxidn. reaction was studied by electrochem., spectroelectrochem., and chromatog. methods on Pd-Ni and Pd-Ag nanoparticules supported on C Vulcan XC 72R. These materials, prepd. by the so-called Bromide Anion Exchange method, exhibited high activity toward the glycerol electrooxidn. in alk. medium showing also an important shift of the onset potential toward low potential values. Electrolysis coupled with HPLC and in situ FTIR spectroscopy (FTIRS) measurements were used to det. the various compds. generated in the oxidative conversion of this three hydroxyl groups C mol. Some products with high added value such as glycerate and tartronate were identified. In situ FTIRS results also showed the pH decrease in the thin layer near the electrode. These results will pos. serve as guidelines for future works on the potential use of glycerol in fuel cell devices in a cogeneration of high value chems. and energy process.
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    White, J.; Anil, A.; Martín-Yerga, D.; Salazar-Alvarez, G.; Henriksson, G.; Cornell, A. Electrodeposited PdNi on a Ni Rotating Disk Electrode Highly Active for Glycerol Electrooxidation in Alkaline Conditions. Electrochim. Acta 2022, 403, 139714,  DOI: 10.1016/j.electacta.2021.139714
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    16
    Electrodeposited PdNi on a Ni rotating disk electrode highly active for glycerol electrooxidation in alkaline conditions
    White, Jai; Anil, Athira; Martin-Yerga, Daniel; Salazar-Alvarez, German; Henriksson, Gunnar; Cornell, Ann
    Electrochimica Acta (2022), 403 (), 139714CODEN: ELCAAV; ISSN:0013-4686. (Elsevier Ltd.)
    The development of alc.-based electrolysis to enable the concurrent prodn. of hydrogen with low electricity consumption still faces major challenges in terms of the max. anodic c.d. achievable. While noble metals enable a low electrode potential to facilitate alc. oxidn., the deactivation of the catalyst at higher potentials makes it difficult for the obtained anodic c.d. to compete with water electrolysis. In this work the effect of significant parameters such as mass transport, glycerol and OH- concn. and electrolyte temp. on the glycerol electrooxidn. reaction (GEOR) in alk. conditions on a bimetallic catalyst PdNi/NiRDE (Pd0.9Ni0.1) has been studied to discern exptl. conditions which maximise achievable anodic c.d. before deactivation occurs. The ratio of NaOH:glycerol in the electrolyte highly affects the rate of the GEOR. A max. c.d. of 793 mA cm-2 at -0.125 V vs. Hg/HgO through steady state polarisation curves was achieved at a moderate and intermediate rotation rate of 500 RPM in a 2 M NaOH and 1 M glycerol (ratio of 2) electrolyte at 80°C. Shown here is a method of catalyst reactivation for enabling the long-term use of the PdNi/NiRDE for electrolysis at optimal conditions for extended periods of time (3 h at 300 mA cm-2 and 10 h at 100 mA cm-2). Through SEM (SEM), X-ray photon electron spectroscopy (XPS) and X-ray diffraction (XRD) it is shown that the electrodeposition of Pd and Ni forms an alloy and that after 10 h of electrolysis the catalyst has chem. and structural stability. This study provides details on parameters significant to the maximising of the GEOR c.d. and the minimising of the debilitating effect that deactivation has on noble metal based electrocatalysts for the GEOR.
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    Koper, M. T. M. Structure Sensitivity and Nanoscale Effects in Electrocatalysis. Nanoscale 2011, 3 (5), 2054– 2073,  DOI: 10.1039/c0nr00857e
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    Structure sensitivity and nanoscale effects in electrocatalysis
    Koper, Marc T. M.
    Nanoscale (2011), 3 (5), 2054-2073CODEN: NANOHL; ISSN:2040-3372. (Royal Society of Chemistry)
    A review discusses the role of the detailed nanoscale structure of catalytic surfaces on the activity of various electrocatalytic reactions of importance for fuel cells, H prodn., and other environmentally important catalytic reactions, such as CO oxidn., MeOH and EtOH oxidn., NH3 oxidn., nitric oxide redn., H evolution, and O redn. Specifically, results and insights obtained from surface-science single-crystal-based model expts. are linked to expts. on well-defined shape-controlled nanoparticles. A classification of structure sensitive effects in electrocatalysis is suggested, based both on empirical grounds and on quantum-chem. viz. thermochem. considerations. The mutual relation between the two classification schemes is also discussed. The review underscores the relevance of single-crystal modeling of nanoscale effects in catalysis, and points to the special role of two kinds of active sites for electrocatalysis on nanoparticulate surfaces: (i) steps and defects in (111) terraces or facets, and (ii) long-range (100) terraces or facets.
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    Li, R.; Wei, Z.; Huang, T.; Yu, A. Ultrasonic-Assisted Synthesis of Pd-Ni Alloy Catalysts Supported on Multi-Walled Carbon Nanotubes for Formic Acid Electrooxidation. Electrochim. Acta 2011, 56 (19), 6860– 6865,  DOI: 10.1016/j.electacta.2011.05.097
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    18
    Ultrasonic-assisted synthesis of Pd-Ni alloy catalysts supported on multi-walled carbon nanotubes for formic acid electrooxidation
    Li, Ruoshi; Wei, Zhen; Huang, Tao; Yu, Aishui
    Electrochimica Acta (2011), 56 (19), 6860-6865CODEN: ELCAAV; ISSN:0013-4686. (Elsevier Ltd.)
    Pd-Ni alloys with different compns. (i.e. Pd2Ni, PdNi, PdNi2) dispersed on multi-walled C nanotubes (MWCNTs) were prepd. by ultrasonic-assisted chem. redn. The XRD patterns indicate that all Pd and Pd-Ni nanoparticles exist as Pd fcc. structure, while Ni alloys with Pd. The TEM images show the addn. of Ni decreases the particle size and improves the dispersion. The XPS spectra demonstrate the electronic modification of Pd by Ni doping. The electrochem. measurements reveal that the PdNi catalysts have better catalytic activity and stability for formic acid electrooxidn., among them PdNi/MWCNTs is the best. The performance enhancement is ascribed to the increase of electroactive surface area (EASA) and Ni doping effect which might modify the electronic structure.
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    Du, C.; Chen, M.; Wang, W.; Yin, G. Nanoporous PdNi Alloy Nanowires As Highly Active Catalysts for the Electro-Oxidation of Formic Acid. ACS Appl. Mater. Interfaces 2011, 3 (2), 105– 109,  DOI: 10.1021/am100803d
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    Nanoporous PdNi Alloy Nanowires As Highly Active Catalysts for the Electro-Oxidation of Formic Acid
    Du, Chunyu; Chen, Meng; Wang, Wengang; Yin, Geping
    ACS Applied Materials & Interfaces (2011), 3 (2), 105-109CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
    Highly active and durable catalysts for formic acid oxidn. are crucial to the development of direct formic acid fuel cell. In this letter, we report the synthesis, characterization, and electrochem. testing of nanoporous Pd57Ni43 alloy nanowires for use as the electrocatalyst towards formic acid oxidn. These nanowires are prepd. by chem. dealloying of Ni from Ni-rich PdNi alloy nanowires, and have high surface area. X-ray diffraction data show that the Pd57Ni43 nanowires have the face-centered cubic cryst. structure of pure Pd, whereas XPS confirms the modification of electronic structure of Pd by electron transfer from Ni to Pd. Electrocatalytic activity of the nanowires towards formic acid oxidn. exceeds that of the state-of-the-art Pd/C. More importantly, the nanowires are highly resistant to deactivation. It is proposed that the high active surface area and modulated surface properties by Ni are responsible for the improvement of activity and durability. Dealloyed nanoporous Pd57Ni43 alloy nanowires are thus proposed as a promising catalyst towards formic acid oxidn.
  20. 20
    López-Coronel, A.; Torres-Pacheco, L. J.; Bañuelos, J. A.; Álvarez-López, A.; Guerra-Balcázar, M.; Álvarez-Contreras, L.; Arjona, N. Highly Active PdNi Bimetallic Nanocubes Electrocatalysts for the Ethylene Glycol Electro-Oxidation in Alkaline Medium. Appl. Surf. Sci. 2020, 530, 147210,  DOI: 10.1016/j.apsusc.2020.147210
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    20
    Highly active PdNi bimetallic nanocubes electrocatalysts for the ethylene glycol electro-oxidation in alkaline medium
    Lopez-Coronel, Andres; Torres-Pacheco, Luis J.; Banuelos, Jennifer A.; Alvarez-Lopez, Alejandra; Guerra-Balcazar, Minerva; Alvarez-Contreras, Lorena; Arjona, Noe
    Applied Surface Science (2020), 530 (), 147210CODEN: ASUSEE; ISSN:0169-4332. (Elsevier B.V.)
    Sub <10 nm PdNi bimetallic nanocubes were used as electrocatalysts for the ethylene glycol electrooxidn. reaction (EGOR) in alk. media. Pd nanocubes were obtained and used as ref. material. Spectroscopic tests indicated that materials labeled as Pd80Ni20/C, Pd70Ni30/C and Pd60Ni40/C were obtained. High-resoln. transmission electron micrographs (HR-TEM) revealed nanocubes-like shapes in all materials, being particularly abundant in Pd80Ni20/C and Pd60Ni40/C. Pd70Ni30/C presented a mixt. of hemispheres and nanocubes. Av. particle sizes of ∼6 nm were detd. for Pd80Ni20/C and Pd60Ni40/C, while Pd70Ni30/C had particle sizes of 5.6 nm. XPS concluded that Ni was as Ni-(oxy) hydroxides (NiOOH), providing oxygenated species in the EGOR and thus, improving the electron transfer, as was corroborated by electrochem. impedance spectroscopy (EIS). In this manner, Pd70Ni30/C and Pd60Ni40/C displayed superior activity at 1 M EG + 2 M KOH than Pd nanocubes and Pd80Ni20/C, achieving current densities close to 320 mA cm-2. The increase of temp. to 50° resulted beneficial for Pd70Ni30/C, displaying a max. c.d. of 501.08 mA cm-2.
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    Guo, M.; Wang, H.; Cui, L.; Zhang, J.; Xiang, Y.; Lu, S. Nickel Promoted Palladium Nanoparticles for Electrocatalysis of Carbohydrazide Oxidation Reaction. Small 2019, 15 (28), 1900929,  DOI: 10.1002/smll.201900929
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    Shen, S. Y.; Zhao, T. S.; Xu, J. B.; Li, Y. S. Synthesis of PdNi Catalysts for the Oxidation of Ethanol in Alkaline Direct Ethanol Fuel Cells. J. Power Sources 2010, 195 (4), 1001– 1006,  DOI: 10.1016/j.jpowsour.2009.08.079
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    Synthesis of PdNi catalysts for the oxidation of ethanol in alkaline direct ethanol fuel cells
    Shen, S. Y.; Zhao, T. S.; Xu, J. B.; Li, Y. S.
    Journal of Power Sources (2010), 195 (4), 1001-1006CODEN: JPSODZ; ISSN:0378-7753. (Elsevier B.V.)
    Carbon-supported PdNi catalysts for the ethanol oxidn. reaction in alk. direct ethanol fuel cells are successfully synthesized by the simultaneous redn. method using NaBH4 as reductant. X-ray diffraction characterization confirms the formation of the face-centered cubic cryst. Pd and Ni(OH)2 on the carbon powder for the PdNi/C catalysts. Transmission electron microscopy images show that the metal particles are well-dispersed on the carbon powder, while energy-dispersive X-ray spectrometer results indicate the uniform distribution of Ni around Pd. XPS analyses reveal the chem. states of Ni, including metallic Ni, NiO, Ni(OH)2 and NiOOH. Cyclic voltammetry and chronopotentiometry tests demonstrate that the Pd2Ni3/C catalyst exhibits higher activity and stability for the ethanol oxidn. reaction in an alk. medium than does the Pd/C catalyst. Fuel cell performance tests show that the application of Pd2Ni3/C as the anode catalyst of an alk. direct ethanol fuel cell with an anion-exchange membrane can yield a max. power d. of 90 mW cm-2 at 60 °C.
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    Miao, B.; Wu, Z.-P.; Zhang, M.; Chen, Y.; Wang, L. Role of Ni in Bimetallic PdNi Catalysts for Ethanol Oxidation Reaction. J. Phys. Chem. C 2018, 122 (39), 22448– 22459,  DOI: 10.1021/acs.jpcc.8b05812
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    Role of Ni in Bimetallic PdNi Catalysts for Ethanol Oxidation Reaction
    Miao, Bei; Wu, Zhi-Peng; Zhang, Minhua; Chen, Yifei; Wang, Lichang
    Journal of Physical Chemistry C (2018), 122 (39), 22448-22459CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    Bimetallic PdNi catalysts have garnered great interest in the study of ethanol oxidn. reactions (EORs), though mechanistic insights into their catalytic performances are lacking, which hinders further improvement and rational design of the next generation of PdNi catalysts. As such, d. functional theory (DFT) calcns. were performed for six key elementary reactions using four model catalysts, one with pure Pd and three for PdNi. DFT results indicate that the reduced catalytic activities obsd. exptl. when Ni atoms were placed under Pd layers are the result of an increase in the reaction barrier for CH3COOH formation. Further anal. illustrated that this is largely owing to the charge transfer from the Ni to the Pd atoms. On the other hand, the enhanced activities of the PdNi catalysts with respect to pure Pd catalysts in EORs when Ni atoms are exposed at the catalyst surfaces are due to the lowering of the reaction barrier toward C-C bond cleavage and increasing of that toward C-O bond coupling. Therefore, surface Ni atoms are responsible for the superior activity of the PdNi catalysts in EORs. Further anal. of DFT results suggests that the reaction barriers of the C-C bond cleavage and the C-O bond coupling approach similar values when the compn. of surface Ni atoms in a PdNi catalyst reaches about 44%. To achieve a complete EOR, the estd. surface Ni atoms should be as high as 77%. However, stability may become a concern for catalysts with such a high exposure of Ni atoms at the catalyst surface.
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    Yang, H.; Wang, H.; Li, H.; Ji, S.; Davids, M. W.; Wang, R. Effect of Stabilizers on the Synthesis of Palladium-Nickel Nanoparticles Supported on Carbon for Ethanol Oxidation in Alkaline Medium. J. Power Sources 2014, 260, 12– 18,  DOI: 10.1016/j.jpowsour.2014.02.110
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    Effect of stabilizers on the synthesis of palladium-nickel nanoparticles supported on carbon for ethanol oxidation in alkaline medium
    Yang, Huijuan; Wang, Hui; Li, Hao; Ji, Shan; Davids, Moegamat Wafeeq; Wang, Rongfang
    Journal of Power Sources (2014), 260 (), 12-18CODEN: JPSODZ; ISSN:0378-7753. (Elsevier B.V.)
    PdNi/C electrocatalysts for ethanol oxidn. in alk. medium are fabricated using four stabilizers, i.e., glycine (G), ethylene diamine tetraacetic acid (EDTA), sodium citrate (SC), and sodium dodecyl sulfate (SDS) with the same reducing process and reaction parameters. X-ray diffraction characterization shows PdNi nanoparticles for all PdNi/C electrocatalysts possess face-centered cubic structure with different alloying degree. TEM results show that PdNi/C-G and PdNi/C-SC have uniform dispersion with ellipse morphol., while particle agglomeration occurs on PdNi/C-EDTA and PdNi/C-SDS. Electrocatalytic activities of these PdNi/C electrocatalysts for ethanol oxidn. are measured by cyclic voltammetry and chronoamperometry techniques. The electrocatalytic activities of PdNi/C change with the different lattice contraction. PdNi/C-SC electrocatalyst exhibits the best activity among the four electrocatalysts, which is ascribed to an appropriate lattice contraction.
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    Dutta, A.; Datta, J. Energy Efficient Role of Ni/NiO in PdNi Nano Catalyst Used in Alkaline DEFC. J. Mater. Chem. A 2014, 2 (9), 3237– 3250,  DOI: 10.1039/c3ta12708g
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    Energy efficient role of Ni/NiO in PdNi nano catalyst used in alkaline DEFC
    Dutta, Abhijit; Datta, Jayati
    Journal of Materials Chemistry A: Materials for Energy and Sustainability (2014), 2 (9), 3237-3250CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
    The present study is based on a study of electrooxidn. of EtOH in alk. medium over the C supported PdxNiy catalyst formulations synthesized by simultaneous redn. of the precursors using Na borohydride as the reducing agent. X-ray diffraction studies of the PdNi/C nano-particles reveal formation of the fcc. cryst. Pd, NiO and Ni(OH)2 on a meso porous C support whereas XPS confirmed the presence of metallic Ni and the oxide phases NiO, Ni(OH)2, NiOOH in the catalyst matrix. The structure and morphol. of the binary matrix and the role of Ni and its oxide as a catalytically contributing entity in the oxidn. process was ascertained by the help of resp. anal. techniques like TEM, XRD, XPS, voltammetry and chronoamperometry. Sequential oxidn. steps were suggested involving dimeric (NiO)2 as one of the intermediate species during the oxidn. reaction proceeding towards aldehyde formation and further to carbonate prodn. via the intermediate formation of a 6 member ring, thereby increasing the reaction rates. This phenomenon was discussed at mol. level using the results obtained from XPS anal. The observations were further accomplished by extending the work to ion chromatog. for quant. anal. of the products formed during oxidn. of EtOH. All the above results are congruent with the mechanistic interpretation and reflect the paramount significance of NiO existing in the binary catalyst matrix for accelerating EtOH oxidn. reaction kinetics at a temp. 40° and above.
  26. 26
    Zhao, Y.; Yang, X.; Tian, J.; Wang, F.; Zhan, L. Methanol Electro-Oxidation on Ni@Pd Core-Shell Nanoparticles Supported on Multi-Walled Carbon Nanotubes in Alkaline Media. Int. J. Hydrogen Energy 2010, 35 (8), 3249– 3257,  DOI: 10.1016/j.ijhydene.2010.01.112
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    Methanol electro-oxidation on Ni@Pd core-shell nanoparticles supported on multi-walled carbon nanotubes in alkaline media
    Zhao, Yanchun; Yang, Xiulin; Tian, Jianniao; Wang, Fengyang; Zhan, Lu
    International Journal of Hydrogen Energy (2010), 35 (8), 3249-3257CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
    A novel method to prep. well-dispersed Ni@Pd core-shell nanoparticles on multi-walled carbon nanotubes (Ni@Pd/MWCNTs) is reported. The morphol. and crystallinity of the catalyst are characterized by SEM, transmission electron microscopy (TEM), XPS and X-ray diffraction (XRD) analyses, resp. Binary composite Ni@Pd/MWCNTs have been obtained and investigated for electrocatalysis of methanol oxidn. in 0.5 M NaOH. It is obsd. that Ni@Pd/MWCNTs increases the apparent electrocatalytic activity and stability of the electrode considerably than that of PdNi/MWCNTs and Pd/MWCNTs catalysts. It is implied that Ni@Pd core-shell nanoparticles supported on MWCNTs is very promising for portable applications in DMFC in alk. soln.
  27. 27
    Araujo, R. B.; Martín-Yerga, D.; Santos, E. C.; Cornell, A.; Pettersson, L. G. M. Elucidating the Role of Ni to Enhance the Methanol Oxidation Reaction on Pd Electrocatalysts. Electrochim. Acta 2020, 360, 136954,  DOI: 10.1016/j.electacta.2020.136954
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    Elucidating the role of Ni to enhance the methanol oxidation reaction on Pd electrocatalysts
    Araujo, Rafael B.; Martin-Yerga, Daniel; Santos, Egon Campos dos; Cornell, Ann; Pettersson, Lars G. M.
    Electrochimica Acta (2020), 360 (), 136954CODEN: ELCAAV; ISSN:0013-4686. (Elsevier Ltd.)
    Amongst promising available technologies enabling the transition to renewable energy sources, electrochem. oxidn. of alcs., in a direct fuel cell or in an electrolysis reaction (H2 prodn.), can be an economically and sustainable alternative to currently used technologies. The authors highlight the advantages of a Pd-Ni bimetallic electrocatalyst for MeOH electrooxidn. - a convenient choice due to the low cost of Ni combined with the obsd. acceptable catalytic performance of Pd. The authors report a synergistic effort between expts. and theor. calcns. based on d. functional theory to provide an in-depth understanding - at the atomistic level - of the origin of the enhanced electrochem. activity of MeOH electrooxidn. using the bimetallic catalysts Pd3Ni and PdNi over pure Pd. Cyclic voltammograms and High-Performance Liq. Chromatog. (HPLC) demonstrate higher activity towards MeOH electrooxidn. with increased Ni concn. and, also, higher selectivity for CO2. These effects are understood by: (1) changes in the MeOH oxidn. reaction mechanism. (2) Mitigation or suppression of CO poisoning on the Pd-Ni alloys as compared to the pure Pd catalyst. (3) A stronger tendency towards highly oxidized intermediates for the alloys. These findings elucidate the effects of a bimetallic electrocatalyst for alc. electrooxidn. as well as unambiguously suggest PdNi as a more cost-effective alternative electrocatalyst.
  28. 28
    Liu, Z.; Zhang, X.; Hong, L. Physical and Electrochemical Characterizations of Nanostructured Pd/C and PdNi/C Catalysts for Methanol Oxidation. Electrochem. Commun. 2009, 11 (4), 925– 928,  DOI: 10.1016/j.elecom.2009.02.030
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    Physical and electrochemical characterizations of nanostructured Pd/C and PdNi/C catalysts for methanol oxidation
    Liu, Zhaolin; Zhang, Xinhui; Hong, Liang
    Electrochemistry Communications (2009), 11 (4), 925-928CODEN: ECCMF9; ISSN:1388-2481. (Elsevier B.V.)
    Pd and PdNi nanoparticles supported on Vulcan XC-72 carbon were prepd. by a chem. redn. with formic acid process. The catalysts were characterized by TEM, XRD, cyclic voltammetry, and chronoamperometry. The Pd and PdNi nanoparticles, which were uniformly dispersed on carbon, were 2-10 nm in diams. The PdNi/C catalyst has higher electrocatalytic activity for methanol oxidn. in alk. media than a comparative Pd/C catalyst and shows great potential as less expensive electrocatalyst for methanol electrooxidn. in alk. media in direct methanol fuel cells.
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    Martín-Yerga, D.; Yu, X.; Terekhina, I.; Henriksson, G.; Cornell, A. In Situ Catalyst Reactivation for Enhancing Alcohol Electro-Oxidation and Coupled Hydrogen Generation. Chem. Commun. 2020, 56 (28), 4011– 4014,  DOI: 10.1039/D0CC01321H
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    In situ catalyst reactivation for enhancing alcohol electro-oxidation and coupled hydrogen generation
    Martin-Yerga, Daniel; Yu, Xiaowen; Terekhina, Irina; Henriksson, Gunnar; Cornell, Ann
    Chemical Communications (Cambridge, United Kingdom) (2020), 56 (28), 4011-4014CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
    A novel method exploiting the in situ reactivation of a PdNi catalyst to enhance the electro-oxidn. of alcs. is reported. The periodic regeneration of the catalyst surface leads to significant gains in terms of conversion rate, energy requirements and stability compared to the conventional potentiostatic method.
  30. 30
    Martín-Yerga, D.; White, J.; Henriksson, G.; Cornell, A. Structure-Reactivity Effects of Biomass-Based Hydroxyacids for Sustainable Electrochemical Hydrogen Production. ChemSusChem 2021, 14 (8), 1902– 1912,  DOI: 10.1002/cssc.202100073
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    Structure-Reactivity Effects of Biomass-based Hydroxyacids for Sustainable Electrochemical Hydrogen Production
    Martin-Yerga, Daniel; White, Jai; Henriksson, Gunnar; Cornell, Ann
    ChemSusChem (2021), 14 (8), 1902-1912CODEN: CHEMIZ; ISSN:1864-5631. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Biomass electro-oxidn. is a promising approach for the sustainable generation of H2 by electrolysis with simultaneous synthesis of value-added chems. In this work, the electro-oxidn. of two structurally different org. hydroxyacids, lactic acid and gluconic acid, was studied comparatively to understand how the chem. structure of the hydroxyacid affects the electrochem. reactivity under various conditions. It was concluded that hydroxyacids such as gluconic acid, with a considerable d. of C-OH groups, are highly reactive and promising for the sustainable generation of H2 by electrolysis at low potentials and high conversion rates (less than -0.15 V vs. Hg/HgO at 400 mA cm-2) but with low selectivity to specific final products. In contrast, the lower reactivity of lactic acid did not enable H2 generation at very high conversion rates (<100 mA cm-2), but the reaction was significantly more selective (64 % to pyruvic acid). This work shows the potential of biomass-based org. hydroxyacids for sustainable generation of H2 and highlights the importance of the chem. structure on the reactivity and selectivity of the electro-oxidn. reactions.
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    Ipadeola, A. K.; Lisa Mathebula, N. Z.; Pagliaro, M. V.; Miller, H. A.; Vizza, F.; Davies, V.; Jia, Q.; Marken, F.; Ozoemena, K. I. Unmasking the Latent Passivating Roles of Ni(OH)2 on the Performance of Pd-Ni Electrocatalysts for Alkaline Ethanol Fuel Cells. ACS Appl. Energy Mater. 2020, 3 (9), 8786– 8802,  DOI: 10.1021/acsaem.0c01314
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    Unmasking the Latent Passivating Roles of Ni(OH)2 on the Performance of Pd-Ni Electrocatalysts for Alkaline Ethanol Fuel Cells
    Ipadeola, Adewale Kabir; Lisa Mathebula, Nomxolisi Zakithi; Pagliaro, Maria Vincenza; Miller, Hamish Andrew; Vizza, Francesco; Davies, Veronica; Jia, Qingying; Marken, Frank; Ozoemena, Kenneth Ikechukwu
    ACS Applied Energy Materials (2020), 3 (9), 8786-8802CODEN: AAEMCQ; ISSN:2574-0962. (American Chemical Society)
    Nicked-based metal-org. framework-derived carbon (Ni/MOFDC) and its acid-treated counterpart (AT-Ni/MOFDC) have been prepd. as supports for palladium nanoparticle electrocatalysts (Pd/Ni/MOFDC and Pd/AT-Ni/MOFDC). These materials have been prepd. using facile microwave-assisted techniques. Several spectroscopic and microscopic techniques (such as FTIR, Raman, PXRD, XPS, XANES, FT-EXAFS, and TEM) have been used to thoroughly characterize physicochem. properties of the materials. It is revealed that acid treatment successfully cleaned the metallic Ni surface of the passivating hydroxides (Ni(OH)2 and NiOOH) to generate a very low concn. of Ni nanoparticles on the carbon support. The Ni-deficient Pd/AT-Ni/MOFDC shows excellent electrocatalytic performance toward ethanol oxidn. reaction (EOR) in the alk. medium compared to the Ni-hydroxide-rich Pd/Ni/MOFDC counterpart. As a proof-of-concept, these electrocatalysts have been employed as anodes and demonstrated for membraneless direct ethanol microfuel cells (μ-DEFCs) with a micro-3D-printed cell, with FeCo/C as electrocatalyst for the oxygen redn. reaction at the cathode. The Pd/AT-Ni/MOFDC displays increased peak power d. (Pm = 26.49 mW cm-2) with 68% voltage retention after a 24 h galvanostatic discharge test at 40 mA cm-2 and reduced impedance. The improved electrocatalytic properties of the Pd/AT-Ni/MOFDC underscore the need to clean the nickel surface of its passivating hydroxides to harness its full promotional activities toward alc. oxidn. reaction on precious metal electrocatalysts.
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    del Rosario, J. A. D.; Ocon, J. D.; Jeon, H.; Yi, Y.; Lee, J. K.; Lee, J. Enhancing Role of Nickel in the Nickel-Palladium Bilayer for Electrocatalytic Oxidation of Ethanol in Alkaline Media. J. Phys. Chem. C 2014, 118 (39), 22473– 22478,  DOI: 10.1021/jp411601c
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    Enhancing Role of Nickel in the Nickel-Palladium Bilayer for Electrocatalytic Oxidation of Ethanol in Alkaline Media
    del Rosario, Julie Anne D.; Ocon, Joey D.; Jeon, Hongrae; Yi, Youngmi; Lee, Jae Kwang; Lee, Jaeyoung
    Journal of Physical Chemistry C (2014), 118 (39), 22473-22478CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    Direct ethanol fuel cells (DEFCs) have been widely studied because of their potential as a high-energy d. and low-toxicity power source of the future. Suitable catalysts for the anode reaction, however, are necessary to fully utilize the advantages of DEFCs. In this paper, we fabricated nickel (Ni)-palladium (Pd) bimetallic catalysts with a bilayer structure, using sputtering deposition on a titanium (Ti) foil substrate, and investigated the activity and stability of the catalysts toward ethanol electro-oxidn. in alk. media. Our results suggest that while Pd is the active component and Ni has negligible activity toward ethanol oxidn., Ni-modified Pd (NiPd/Ti) provides the best activity in comparison to PdNi/Ti and the monometallic catalysts. In fact, optimizing the Ni amt. could lead to a highly active and stable bimetallic electrocatalyst because of Ni's ability to increase the active surface area of the Pd layer, provide hydroxyl species to replenish the active sites, and act as a protective layer to the Pd. Overall, these results provide a better understanding on the role of Ni in bimetallic catalysts, esp. in a bilayer configuration, to allow the use of an ethanol oxidn. reaction (EOR)-active electrocatalyst with a much lower Pd content.
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    White, J.; Peters, L.; Martín-Yerga, D.; Terekhina, I.; Anil, A.; Lundberg, H.; Johnsson, M.; Salazar-Alvarez, G.; Henriksson, G.; Cornell, A. Glycerol Electrooxidation at Industrially Relevant Current Densities Using Electrodeposited PdNi/Nifoam Catalysts in Aerated Alkaline Media. J. Electrochem. Soc. 2023, 170 (8), 086504,  DOI: 10.1149/1945-7111/acee27
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    Hiltrop, D.; Cychy, S.; Elumeeva, K.; Schuhmann, W.; Muhler, M. Spectroelectrochemical Studies on the Effect of Cations in the Alkaline Glycerol Oxidation Reaction over Carbon Nanotube-Supported Pd Nanoparticles. Beilstein J. Org. Chem. 2018, 14 (1), 1428– 1435,  DOI: 10.3762/bjoc.14.120
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    Spectroelectrochemical studies on the effect of cations in the alkaline glycerol oxidation reaction over carbon nanotube-supported Pd nanoparticles
    Hiltrop Dennis; Cychy Steffen; Muhler Martin; Elumeeva Karina; Schuhmann Wolfgang
    Beilstein journal of organic chemistry (2018), 14 (), 1428-1435 ISSN:1860-5397.
    The effects of the alkali cations Na(+) and K(+) were investigated in the alkaline electrochemical oxidation of glycerol over Pd nanoparticles (NPs) deposited on functionalized carbon nanotubes (CNTs). The electrocatalytic activity was assessed by cyclic voltammetry revealing a lower overpotential of glycerol oxidation for nitrogen-functionalized Pd/NCNTs compared with oxygen-functionalized Pd/OCNTs. Whereas significantly lower current densities were observed for Pd/OCNT in NaOH than in KOH in agreement with stronger non-covalent interactions on the Pd surface, Pd/NCNT achieved an approximately three-times higher current density in NaOH than in KOH. In situ electrochemistry/IR spectroscopy was applied to unravel the product distribution as a function of the applied potential in NaOH and KOH. The IR spectra exhibited strongly changing band patterns upon varying the potential between 0.77 and 1.17 V vs RHE: at low potentials oxidized C3 species such as mesoxalate and tartronate were formed predominantly, and with increasing potentials C2 and C1 species originating from C-C bond cleavage were identified. The tendency to produce carbonate was found to be less pronounced in KOH. The less favored formation of highly oxidized C3 species and of carbonate is deduced to be the origin of the lower current densities in the cyclic voltammograms (CVs) for Pd/NCNT in KOH. The enhanced current densities in NaOH are rationalized by the presence of Na(+) ions bound to the basic nitrogen species in the NCNT support. Adsorbed Na(+) ions can form complexes with the organic molecules, presumably enhanced by the chelate effect. In this way, the organic molecules are assumed to be bound more tightly to the NCNT support in close proximity to the Pd NPs facilitating their oxidation.
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    Rahim, S. A. N. M.; Lee, C. S.; Abnisa, F.; Aroua, M. K.; Daud, W. A. W.; Cognet, P.; Pérès, Y. A Review of Recent Developments on Kinetics Parameters for Glycerol Electrochemical Conversion - A by-Product of Biodiesel. Sci. Total Environ. 2020, 705, 135137,  DOI: 10.1016/j.scitotenv.2019.135137
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    A review of recent developments on kinetics parameters for glycerol electrochemical conversion - A by-product of biodiesel
    Rahim, Siti Aqilah Nadhirah Md.; Lee, Ching Shya; Abnisa, Faisal; Aroua, Mohamed Kheireddine; Daud, Wan Ashri Wan; Cognet, Patrick; Peres, Yolande
    Science of the Total Environment (2020), 705 (), 135137CODEN: STENDL; ISSN:0048-9697. (Elsevier B.V.)
    A review. Glycerol is a byproduct produced from biodiesel, fatty acid, soap and bioethanol industries. Today, the value of glycerol is decreasing in the global market due to glycerol surplus, which primarily resulted from the speedy expansion of biodiesel producers around the world. Numerous studies proposed ways of managing and treating glycerol, as well as converting it into value-added compds. The electrochem. conversion method is preferred for this transformation due to its simplicity and hence, it is discussed. Addnl., the factors that could affect the process mechanisms and products distribution in the electrochem. process, including electrodes materials, pH of electrolyte, applied potential, c.d., temp. and additives are also thoroughly explained. Value-added compds. that can be produced from the electrochem. conversion of glycerol include glyceraldehyde, dihydroxyacetone, glycolic acid, glyceric acid, lactic acid, 1,2-propanediol, 1,3-propanediol, tartronic acid and mesoxalic acid. These compds. have broad applications in cosmetics, pharmaceutical, food and polymer industries are also described. This review will be devoted to a comprehensive overview of the current scenario in the glycerol electrochem. conversion, the factors affecting the mechanism pathways, reaction rates, product selectivity and yield. Possible outcomes obtained from the process and their benefits to the industries are discussed. The use of solid acid catalysts as additives for future studies is also suggested.
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    Rodrigues, T. S.; Zhao, M.; Yang, T.-H.; Gilroy, K. D.; da Silva, A. G. M.; Camargo, P. H. C.; Xia, Y. Synthesis of Colloidal Metal Nanocrystals: A Comprehensive Review on the Reductants. Chem.─Eur. J. 2018, 24 (64), 16944– 16963,  DOI: 10.1002/chem.201802194
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    Synthesis of Colloidal Metal Nanocrystals: A Comprehensive Review on the Reductants
    Rodrigues, Thenner S.; Zhao, Ming; Yang, Tung-Han; Gilroy, Kyle D.; da Silva, Anderson G. M.; Camargo, Pedro H. C.; Xia, Younan
    Chemistry - A European Journal (2018), 24 (64), 16944-16963CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
    There is a growing interest in controlling the synthesis of colloidal metal nanocrystals and thus tailoring their properties toward various applications. In this context, choosing an appropriate combination of reagents (e.g., salt precursor, reductant, capping agent, and stabilizer) plays a pivotal role in enabling the synthesis of metal nanocrystals with diversified sizes, shapes, and structures. Here we present a comprehensive review that highlights one of the key reagents for the synthesis of metal nanocrystals via chem. redn.: the reductants. We start with a brief introduction to the compds. commonly employed as reductants in the colloidal synthesis of metal nanocrystals by showing their oxidn. half-reactions and the corresponding oxidn. potentials. Then we offer specific examples pertaining to the controlled synthesis of metal nanocrystals, followed by some fundamental aspects covering the general mechanisms of metal ion redn. based on the Marcus Theory. Afterwards, we present a case-by-case discussion on a wide variety of reductants, including their major properties, redn. mechanisms, and addnl. effects on the final products. We illustrate these aspects by selecting key examples from the literature and paying close attention to the underlying mechanism in each case. At the end, we conclude by summarizing the highlights of the review and providing some perspectives on future directions.
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    Poerwoprajitno, A. R.; Gloag, L.; Cheong, S.; Gooding, J. J.; Tilley, R. D. Synthesis of Low- and High-Index Faceted Metal (Pt, Pd, Ru, Ir, Rh) Nanoparticles for Improved Activity and Stability in Electrocatalysis. Nanoscale 2019, 11 (41), 18995– 19011,  DOI: 10.1039/C9NR05802H
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    Synthesis of low- and high-index faceted metal (Pt, Pd, Ru, Ir, Rh) nanoparticles for improved activity and stability in electrocatalysis
    Poerwoprajitno, Agus R.; Gloag, Lucy; Cheong, Soshan; Gooding, J. Justin; Tilley, Richard D.
    Nanoscale (2019), 11 (41), 18995-19011CODEN: NANOHL; ISSN:2040-3372. (Royal Society of Chemistry)
    A review. Driven by the quest for future energy soln., faceted metal nanoparticles are being pursued as the next generation electrocatalysts for renewable energy applications. Thanks to recent advancement in soln. phase synthesis, different low- and high-index facets on metal nanocrystals become accessible and are tested for specific electrocatalytic reactions. This minireview summarises the key approaches to prep. nanocrystals contg. the most catalytically active platinum group metals (Pt, Pd, Ru, Ir and Rh) exposed with low- and high-index facets using soln. phase synthesis. Electrocatalytic studies related to the different facets are highlighted to emphasize the importance of exposing facets for catalyzing these reactions, namely oxygen redn. reaction (ORR), hydrogen oxidn. reaction (HOR), alc. oxidn. including methanol (MOR) and ethanol oxidn. reactions (EOR), formic acid oxidn. reaction (FAOR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). The future outlook discusses the challenges and opportunities for making electrocatalysts that are even more active and stable.
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    Gilroy, K. D.; Ruditskiy, A.; Peng, H.-C.; Qin, D.; Xia, Y. Bimetallic Nanocrystals: Syntheses, Properties, and Applications. Chem. Rev. 2016, 116 (18), 10414– 10472,  DOI: 10.1021/acs.chemrev.6b00211
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    Bimetallic Nanocrystals: Syntheses, Properties, and Applications
    Gilroy, Kyle D.; Ruditskiy, Aleksey; Peng, Hsin-Chieh; Qin, Dong; Xia, Younan
    Chemical Reviews (Washington, DC, United States) (2016), 116 (18), 10414-10472CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    Achieving mastery over the synthesis of metal nanocrystals has emerged as one of the foremost scientific endeavors in recent years. This intense interest stems from the fact that the compn., size, and shape of nanocrystals not only define their overall physicochem. properties but also det. their effectiveness in technol. important applications. Our aim is to present a comprehensive review of recent research activities on bimetallic nanocrystals. We begin with a brief introduction to the architectural diversity of bimetallic nanocrystals, followed by discussion of the various synthetic techniques necessary for controlling the elemental ratio and spatial arrangement. We have selected key examples from the literature that exemplify crit. concepts and place a special emphasis on mechanistic understanding. We then discuss the compn.-dependent properties of bimetallic nanocrystals in terms of catalysis, optics, and magnetism and conclude the Review by highlighting applications that have been enabled and/or enhanced by precisely controlling the synthesis of bimetallic nanocrystals.
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    Göksu, H.; Ho, S. F.; Metin, O. ̈.; Korkmaz, K.; Mendoza Garcia, A.; Gültekin, M. S.; Sun, S. Tandem Dehydrogenation of Ammonia Borane and Hydrogenation of Nitro/Nitrile Compounds Catalyzed by Graphene-Supported NiPd Alloy Nanoparticles. ACS Catal. 2014, 4 (6), 1777– 1782,  DOI: 10.1021/cs500167k
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    Tandem Dehydrogenation of Ammonia Borane and Hydrogenation of Nitro/Nitrile Compounds Catalyzed by Graphene-Supported NiPd Alloy Nanoparticles
    Goksu, Haydar; Ho, Sally Fae; Metin, Onder; Korkmaz, Katip; Mendoza Garcia, Adriana; Gultekin, Mehmet Serdar; Sun, Shouheng
    ACS Catalysis (2014), 4 (6), 1777-1782CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
    Nickel-palladium alloy nanoparticles supported on graphene were prepd. and used as catalysts for the chemoselective transfer hydrogenation reactions of nitro compds. and nitriles using ammonia-borane as the stoichiometric reductant. Of the graphene-supported nanoparticles prepd., the graphene-supported Ni30Pd70 nanoparticles were the most active. In the presence of graphene-supported Ni30Pd70 nanoparticles and ammonia-borane, aryl nitro compds., nitromethane, and nitroethane were hydrogenated to the corresponding amines in >99% yields and in 5-30 min at ambient temp. Aryl nitriles, propanenitrile, and isobutyronitrile were reduced to primary amines in 90->99% yields in 5-720 min at ambient temps.; nitro-substituted aryl nitriles were reduced chemoselectively to amino nitriles.
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    Hummelgård, C.; Karlsson, R. K. B.; Bäckström, J.; Rahman, S. M. H.; Cornell, A.; Eriksson, S.; Olin, H. Physical and Electrochemical Properties of Cobalt Doped (Ti,Ru)O2 Electrode Coatings. Mater. Sci. Eng. B 2013, 178 (20), 1515– 1522,  DOI: 10.1016/j.mseb.2013.08.018
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    Bolzán, A. Phenomenological Aspects Related to the Electrochemical Behaviour of Smooth Palladium Electrodes in Alkaline Solutions. J. Electroanal. Chem. 1995, 380 (1–2), 127– 138,  DOI: 10.1016/0022-0728(94)03627-F
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    Phenomenological aspects related to the electrochemical behavior of smooth palladium electrodes in alkaline solutions
    Bolzan, A. E.
    Journal of Electroanalytical Chemistry (1995), 380 (1-2), 127-38CODEN: JECHES ISSN:. (Elsevier)
    The voltammetric behavior of smooth palladium electrodes in 1M NaOH was studied in the potential range related to the thermodn. stability of water. The electrosorption of H atoms on bulk Pd appears as a reversible reaction coupled to a diffusion process which occurs within bulk Pd. The voltammetric electrodesorption of H from bulk Pd is a process under mixed control, i.e. the diffusion from the bulk and the surface oxidn. of H atoms. Fast pseudocapacitive reactions are detected in the range 0.2-0.4 V assocd. with the adsorption of H atoms at the submonolayer level. The initial stages of Pd oxide layer formation, at ∼0.68 V, involves two reversible stages. The Pd oxide monolayer formation is achieved at 1.25 V/RHE and is followed by the formation of a 3rd reversible system. This system is enhanced by an excursion in the potential range of the oxygen evolution reaction. This reversible system is probably a redox system involving Pd(II)/Pd(IV) species. The voltammetric electroredn. of the Pd oxide film shows rather irreversible behavior. Inhibition effects on the reversible adsorption of H atoms due to residual oxide species were obsd. as well as inhibition on loading the Pd electrode with hydrogen to form the (α+β)-PdH phase. Rotating ring-disk expts. demonstrate that Pd electrodissoln. in basic solns. is much smaller than in acid solns. However, sol. palladium species are detected, esp. during the formation of the fast redox systems, in the potential range related to Pd oxide layer growth.
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    Breiter, M. W. Dissolution and Adsorption of Hydrogen at Smooth Pd Wires of the Alpha Phase in Sulfuric Acid Solution. J. Electroanal. Chem. 1977, 81 (2), 275– 284,  DOI: 10.1016/S0022-0728(77)80023-5
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    Dissolution and adsorption of hydrogen at smooth palladium wires at potentials of the alpha phase in sulfuric acid solution
    Breiter, M. W.
    Journal of Electroanalytical Chemistry and Interfacial Electrochemistry (1977), 81 (2), 275-84CODEN: JEIEBC; ISSN:0022-0728.
    After decreasing the electrode potential rapidly from 0.7 V, H atoms were allowed to diffuse into Pd wires for 10 or 1 s at const. potential in the region of the α phase. Subsequently the anodic current due to H removal at 0.7 V was recorded by the oscilloscope. The current decays after a certain time according to a law characteristic for the diffusion of H from the interior of the Pd wire to the surface as rate-controlling process. The bulk concn. SCH of H atoms directly below the surface was computed on the basis of the diffusion process. The amt. QH of H adsorbed on the surface was detd. as the difference between the integral charge Q from the exptl. current-time curves and the integral charge Q' computed for the diffusion process within a suitable interval of time. The dependence of the bulk concn. SCH and of the H coverage QH upon potential were established and discussed.
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    Chierchie, T.; Mayer, C.; Lorenz, W. J. Structural Changes of Surface Oxide Layers on Palladium. J. Electroanal. Chem. 1982, 135, 211– 220,  DOI: 10.1016/0368-1874(82)85121-6
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    Structural changes of surface oxide layers on palladium
    Chierchie, T.; Mayer, C.; Lorenz, W. J.
    Journal of Electroanalytical Chemistry and Interfacial Electrochemistry (1982), 135 (2), 211-20CODEN: JEIEBC; ISSN:0022-0728.
    The anodic formation of oxide layers on Pd and their cathodic redn. were investigated in HClO4 solns. using cyclic voltammetry and linear sweep polarization. The structure of the voltammograms depends on the anodic polarization and the polarization routine, but less on the sweep rate. From the measured cathodic charge amts. of the redn. as function of these parameters, it is assumed that slow structural changes of the oxide layer occur.
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    Hjorth Larsen, A.; Jørgen Mortensen, J.; Blomqvist, J.; Castelli, I. E.; Christensen, R.; Dułak, M.; Friis, J.; Groves, M. N.; Hammer, B.; Hargus, C.; Hermes, E. D.; Jennings, P. C.; Bjerre Jensen, P.; Kermode, J.; Kitchin, J. R.; Leonhard Kolsbjerg, E.; Kubal, J.; Kaasbjerg, K.; Lysgaard, S.; Bergmann Maronsson, J.; Maxson, T.; Olsen, T.; Pastewka, L.; Peterson, A.; Rostgaard, C.; Schiøtz, J.; Schütt, O.; Strange, M.; Thygesen, K. S.; Vegge, T.; Vilhelmsen, L.; Walter, M.; Zeng, Z.; Jacobsen, K. W. The Atomic Simulation Environment-a Python Library for Working with Atoms. J. Phys.: Condens. Matter 2017, 29 (27), 273002,  DOI: 10.1088/1361-648X/aa680e
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    The atomic simulation environment-a Python library for working with atoms
    Hjorth Larsen Ask; Jorgen Mortensen Jens; Blomqvist Jakob; Castelli Ivano E; Christensen Rune; Dulak Marcin; Friis Jesper; Groves Michael N; Hammer Bjork; Hargus Cory; Hermes Eric D; Jennings Paul C; Bjerre Jensen Peter; Kermode James; Kitchin John R; Leonhard Kolsbjerg Esben; Kubal Joseph; Kaasbjerg Kristen; Lysgaard Steen; Bergmann Maronsson Jon; Maxson Tristan; Olsen Thomas; Pastewka Lars; Peterson Andrew; Rostgaard Carsten; Schiotz Jakob; Schutt Ole; Strange Mikkel; Thygesen Kristian S; Vegge Tejs; Vilhelmsen Lasse; Walter Michael; Zeng Zhenhua; Jacobsen Karsten W
    Journal of physics. Condensed matter : an Institute of Physics journal (2017), 29 (27), 273002 ISSN:.
    The atomic simulation environment (ASE) is a software package written in the Python programming language with the aim of setting up, steering, and analyzing atomistic simulations. In ASE, tasks are fully scripted in Python. The powerful syntax of Python combined with the NumPy array library make it possible to perform very complex simulation tasks. For example, a sequence of calculations may be performed with the use of a simple 'for-loop' construction. Calculations of energy, forces, stresses and other quantities are performed through interfaces to many external electronic structure codes or force fields using a uniform interface. On top of this calculator interface, ASE provides modules for performing many standard simulation tasks such as structure optimization, molecular dynamics, handling of constraints and performing nudged elastic band calculations.
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    Kresse, G.; Furthmüller, J. Efficient Iterative Schemes for Ab Initio Total-Energy Calculations Using a Plane-Wave Basis Set. Phys. Rev. B 1996, 54 (16), 11169– 11186,  DOI: 10.1103/PhysRevB.54.11169
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    Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set
    Kresse, G.; Furthmueller, J.
    Physical Review B: Condensed Matter (1996), 54 (16), 11169-11186CODEN: PRBMDO; ISSN:0163-1829. (American Physical Society)
    The authors present an efficient scheme for calcg. the Kohn-Sham ground state of metallic systems using pseudopotentials and a plane-wave basis set. In the first part the application of Pulay's DIIS method (direct inversion in the iterative subspace) to the iterative diagonalization of large matrixes will be discussed. This approach is stable, reliable, and minimizes the no. of order Natoms3 operations. In the second part, we will discuss an efficient mixing scheme also based on Pulay's scheme. A special "metric" and a special "preconditioning" optimized for a plane-wave basis set will be introduced. Scaling of the method will be discussed in detail for non-self-consistent and self-consistent calcns. It will be shown that the no. of iterations required to obtain a specific precision is almost independent of the system size. Altogether an order Natoms2 scaling is found for systems contg. up to 1000 electrons. If we take into account that the no. of k points can be decreased linearly with the system size, the overall scaling can approach Natoms. They have implemented these algorithms within a powerful package called VASP (Vienna ab initio simulation package). The program and the techniques have been used successfully for a large no. of different systems (liq. and amorphous semiconductors, liq. simple and transition metals, metallic and semiconducting surfaces, phonons in simple metals, transition metals, and semiconductors) and turned out to be very reliable.
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    Wellendorff, J.; Lundgaard, K. T.; Møgelhøj, A.; Petzold, V.; Landis, D. D.; Nørskov, J. K.; Bligaard, T.; Jacobsen, K. W. Density Functionals for Surface Science: Exchange-Correlation Model Development with Bayesian Error Estimation. Phys. Rev. B 2012, 85 (23), 235149,  DOI: 10.1103/PhysRevB.85.235149
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    Density functionals for surface science: exchange-correlation model development with Bayesian error estimation
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    Physical Review B: Condensed Matter and Materials Physics (2012), 85 (23), 235149/1-235149/23CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
    A methodol. for semiempirical d. functional optimization, using regularization and cross-validation methods from machine learning, is developed. We demonstrate that such methods enable well-behaved exchange-correlation approxns. in very flexible model spaces, thus avoiding the overfitting found when std. least-squares methods are applied to high-order polynomial expansions. A general-purpose d. functional for surface science and catalysis studies should accurately describe bond breaking and formation in chem., solid state physics, and surface chem., and should preferably also include van der Waals dispersion interactions. Such a functional necessarily compromises between describing fundamentally different types of interactions, making transferability of the d. functional approxn. a key issue. We investigate this trade-off between describing the energetics of intramol. and intermol., bulk solid, and surface chem. bonding, and the developed optimization method explicitly handles making the compromise based on the directions in model space favored by different materials properties. The approach is applied to designing the Bayesian error estn. functional with van der Waals correlation (BEEF-vdW), a semilocal approxn. with an addnl. nonlocal correlation term. Furthermore, an ensemble of functionals around BEEF-vdW comes out naturally, offering an est. of the computational error. An extensive assessment on a range of data sets validates the applicability of BEEF-vdW to studies in chem. and condensed matter physics. Applications of the approxn. and its Bayesian ensemble error est. to two intricate surface science problems support this.
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    Anil, A.; White, J.; Campos dos Santos, E.; Terekhina, I.; Johnsson, M.; Pettersson, L. G. M.; Cornell, A.; Salazar-Alvarez, G. Effect of Pore Mesostructure on the Electrooxidation of Glycerol on Pt Mesoporous Catalysts. J. Mater. Chem. A 2023, 11 (31), 16570– 16577,  DOI: 10.1039/D3TA01738A
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    Effect of pore mesostructure on the electrooxidation of glycerol on Pt mesoporous catalysts
    Anil, Athira; White, Jai; Campos dos Santos, Egon; Terekhina, Irina; Johnsson, Mats; Pettersson, Lars G. M.; Cornell, Ann; Salazar-Alvarez, German
    Journal of Materials Chemistry A: Materials for Energy and Sustainability (2023), 11 (31), 16570-16577CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
    Glycerol is a renewable chem. that has become widely available and inexpensive owing to the increased prodn. of biodiesel. Noble metal materials are effective catalysts for the prodn. of hydrogen and value-added products through the electrooxidn. of glycerol. In this study, we developed three platinum systems with distinct pore mesostructures, e.g., hierarchical pores (HP), cubic pores (CP) and linear pores (LP), all with high electrochem. active surface area (ECSA). The ECSA-normalized GEOR catalytic activity of the systems follows HPC > LPC > CPC > com. Pt/C. Regarding the oxidn. products, we observe glyceric acid as the main three-carbon product (C3), with oxalic acids as the main two-carbon oxidn. product. DFT-based theor. calcns. support the glyceraldehyde route going through tartronic acid toward oxalic acid and also help in understanding why the dihydroxyacetone (DHA) route is active despite the absence of DHA amongst the obsd. oxidn. products.
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    dos Santos, E. C.; Araujo, R. B.; Valter, M.; Salazar-Alvarez, G.; Johnsson, M.; Bajdich, M.; Abild-Pedersen, F.; Pettersson, L. G. M. Efficient Screening of Bi-Metallic Electrocatalysts for Glycerol Valorization. Electrochim. Acta 2021, 398, 139283,  DOI: 10.1016/j.electacta.2021.139283
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    Efficient Screening of Bi-Metallic Electrocatalysts for Glycerol Valorization
    dos Santos, Egon Campos; Araujo, Rafael B.; Valter, Mikael; Salazar-Alvarez, German; Johnsson, Mats; Bajdich, Michal; Abild-Pedersen, Frank; Pettersson, Lars Gunnar Moody
    Electrochimica Acta (2021), 398 (), 139283CODEN: ELCAAV; ISSN:0013-4686. (Elsevier Ltd.)
    Glycerol is a byproduct of biodiesel prodn. and, as such, it is of limited economic value. By electrooxidn., glycerol can be used as a feedstock for scalable H prodn., in addn. to conversion to value-added products. The development of novel and efficient catalytic electrode materials for the anodic side of the reaction is a key towards a H-based energy economy. A computational screening protocol combining DFT, scaling relations, and microkinetic modeling allows for a rational selection of novel catalysts that can deliver efficient glycerol electrooxidn., low cost of prodn., and environmental sustainability. Activity and chem. selectivity towards H prodn. on pure metal catalysts is discussed in terms of volcano-shaped plots. The selectivity in the glycerol oxidn. reaction is influenced by a different energy landscape when in the presence of H2O and best classified by a comparison of O-H and C-H bond-breaking barriers. The authors screened 3570 bi-metallic catalysts in the AB (L10) and A3B (L12) ordered structures for activity, stability, price, and toxicity. By filtering based on the criteria for toxicity, resistance to oxidn., miscibility, and price, the authors have identified 5 L10 structured catalysts (AgPd, AuPd, PtSb, CuPt, and AgPt) and 20 L12 catalysts (Ga3Ta, In3Ta, Ir3W, Ir3Mo, Cu3Pt, Ir3Ta, Ir3Re, Pd3Bi, Pd3Cu, Pd3W, Pd3Co, Pd3Sn, Pd3Mo, Pd3Ag, Pd3Ga, Pd3Ta, Au3Ru, Pd3In, Au3Ir, and Pd3Au) that are all predicted to show high activity. The authors also identify an addnl. 37 L10 and 92 L12 structured electrocatalysts with an anticipated medium-high activity.
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    Mathew, K.; Sundararaman, R.; Letchworth-Weaver, K.; Arias, T. A.; Hennig, R. G. Implicit Solvation Model for Density-Functional Study of Nanocrystal Surfaces and Reaction Pathways. J. Chem. Phys. 2014, 140 (8), 084106,  DOI: 10.1063/1.4865107
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    Implicit solvation model for density-functional study of nanocrystal surfaces and reaction pathways
    Mathew, Kiran; Sundararaman, Ravishankar; Letchworth-Weaver, Kendra; Arias, T. A.; Hennig, Richard G.
    Journal of Chemical Physics (2014), 140 (8), 084106/1-084106/8CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
    Solid-liq. interfaces are at the heart of many modern-day technologies and provide a challenge to many materials simulation methods. A realistic first-principles computational study of such systems entails the inclusion of solvent effects. We implement an implicit solvation model that has a firm theor. foundation into the widely used d.-functional code Vienna ab initio Software Package. The implicit solvation model follows the framework of joint d. functional theory. We describe the framework, our algorithm and implementation, and benchmarks for small mol. systems. We apply the solvation model to study the surface energies of different facets of semiconducting and metallic nanocrystals and the SN2 reaction pathway. Solvation reduces the surface energies of the nanocrystals, esp. for the semiconducting ones and increases the energy barrier of the SN2 reaction. (c) 2014 American Institute of Physics.
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    Nørskov, J. K.; Rossmeisl, J.; Logadottir, A.; Lindqvist, L.; Kitchin, J. R.; Bligaard, T.; Jónsson, H. Origin of the Overpotential for Oxygen Reduction at a Fuel-Cell Cathode. J. Phys. Chem. B 2004, 108 (46), 17886– 17892,  DOI: 10.1021/jp047349j
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    Origin of the Overpotential for Oxygen Reduction at a Fuel-Cell Cathode
    Norskov, J. K.; Rossmeisl, J.; Logadottir, A.; Lindqvist, L.; Kitchin, J. R.; Bligaard, T.; Jonsson, H.
    Journal of Physical Chemistry B (2004), 108 (46), 17886-17892CODEN: JPCBFK; ISSN:1520-6106. (American Chemical Society)
    A method to obtain the stability of reaction intermediates of electrochem. processes using electronic structure calcns. is presented. This method is used in combination with detailed d. functional calcns. to develop a detailed description of the free-energy landscape of the electrochem. O redn. reaction over Pt(111), as a function of applied bias. This allowed identification of the origin of the overpotential of this reaction. Adsorbed O and hydroxyl are stable intermediates at potentials close to equil., and the calcd. rate const. for the activated p/electron transfer to adsorbed O or hydroxyl can account quant. for the obsd. kinetics. From a database of calcd. O and hydroxyl adsorption energies, the trends in the O redn. rate for a large no. of different transition and noble metals can be explained. Alternative reaction mechanisms involving p/electron transfer to adsorbed mol. O were also considered, and this peroxide mechanism dominates for most noble metals. The model suggests ways to improve the electrocatalytic properties of fuel cell cathodes.
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    Sen, B.; Kuzu, S.; Demir, E.; Yıldırır, E.; Sen, F. Highly Efficient Catalytic Dehydrogenation of Dimethyl Ammonia Borane via Monodisperse Palladium-Nickel Alloy Nanoparticles Assembled on PEDOT. Int. J. Hydrogen Energy 2017, 42 (36), 23307– 23314,  DOI: 10.1016/j.ijhydene.2017.05.115
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    Highly efficient catalytic dehydrogenation of dimethyl ammonia borane via monodisperse palladium-nickel alloy nanoparticles assembled on PEDOT
    Sen, Betul; Kuzu, Sultan; Demir, Enes; Yildirir, Eyup; Sen, Fatih
    International Journal of Hydrogen Energy (2017), 42 (36), 23307-23314CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
    Addressed herein, the synthesis of the monodisperse poly(3,4-ethylenedioxythiophene)(PEDOT) supported palladium-nickel nanomaterials (3.32 ± 0.36 nm) and their applications as a catalyst in dimethylamine-borane (DMAB) dehydrogenation is outlined. Microwave assistance procedure was used in prepn. of nanomaterials where palladium and cobalt cations were reduced in PEDOT soln. (Pd-Ni@PEDOT) in microwave conditions. The characterization of the nanocatalyst was performed by using UV-VIS, XRD, XPS, TEM and HR-TEM-EELS analyses. The Pd-Ni@PEDOT NPs were found to be highly effective and stable for the dehydrogenation of DMAB. The catalytic activity of Pd-Ni@PEDOT was one of the highest one among the all prepd. catalysts in literature even at lower temps. and concns., yielding to give high turnover frequency (451.2 h-1) and low Ea (50.78 ± 2 kJ/mol) for dehydrocoupling of DMAB.
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    Matin, M. A.; Jang, J.-H.; Kwon, Y.-U. PdM Nanoparticles (M = Ni, Co, Fe, Mn) with High Activity and Stability in Formic Acid Oxidation Synthesized by Sonochemical Reactions. J. Power Sources 2014, 262, 356– 363,  DOI: 10.1016/j.jpowsour.2014.03.109
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    PdM nanoparticles (M = Ni, Co, Fe, Mn) with high activity and stability in formic acid oxidation synthesized by sonochemical reactions
    Matin, Md. Abdul; Jang, Ji-Hoon; Kwon, Young-Uk
    Journal of Power Sources (2014), 262 (), 356-363CODEN: JPSODZ; ISSN:0378-7753. (Elsevier B.V.)
    Bimetallic alloy PdnM (n = 1 for M = Mn, Fe, and Co; n = 1, 2, and 3 for M = Ni) nanoparticles (NPs) are synthesized on carbon supports by sonochem. reactions of Pd(acac)2 (acac = acetylacetonate) with M(acac)2 (M = Ni, Co, Mn) or Fe(acac)3 in ethylene glycol. The NPs are characterized by powder X-ray diffractometry, transmission electron microscopy (TEM), and inductively coupled plasma-at. emission spectroscopy to det. their crystal structures, particle sizes, morphol., and elemental compns. Alloy formation of the NPs is proven by energy dispersive X-ray spectroscopy line profiles using scanning TEM. The electronic structures and the surface compns. of NPs are analyzed using XPS and Fourier-transform IR spectroscopy, resp. PdnM NPs are applied as electrocatalysts for formic acid oxidn. The incorporation of M in Pd reduces the poisoning by surface hydroxyl groups. Activities based on the current densities are in the order of PdNi > PdFe > PdCo > PdMn. Within the PdnNi series, the activity is in the order of PdNi > Pd2Ni > Pd3Ni. The PdnM NP electrocatalysts show higher activity by a factor of 2-3.5 and improved durability than similarly prepd. Pd NP electrocatalyst.
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    Khan, M. S.; Khattak, R.; Khan, A.; Chen, Q.; Nisar, J.; Iqbal, Z.; Rashid, A.; Kamran, A. W.; Zekker, I.; Zahoor, M.; Alzahrani, K. J.; Batiha, G. E.-S. Synthesis and Characterizations of PdNi Carbon Supported Nanomaterials: Studies of Electrocatalytic Activity for Oxygen Reduction in Alkaline Medium. Molecules 2021, 26 (11), 3440,  DOI: 10.3390/molecules26113440
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    Synthesis and characterizations of PdNi carbon supported nanomaterials: studies of electrocatalytic activity for oxygen reduction in alkaline medium
    Khan, Muhammad Sufaid; Khattak, Rozina; Khan, Abbas; Chen, Qiuling; Nisar, Jan; Iqbal, Zahoor; Rashid, Abdur; Abdul Waheed Kamran; Zekker, Ivar; Zahoor, Muhammad; Alzahrani, Khalid J.; El-Saber Batiha, Gaber
    Molecules (2021), 26 (11), 3440CODEN: MOLEFW; ISSN:1420-3049. (MDPI AG)
    Electrocatalytic materials offer numerous benefits due to their wide range of applications. In this study, a polyol technique was used to synthesize PdNi nanoparticles (NPs) with different percent at. compns. (Pd = 50 to 90%) to explore their catalytic efficiency. The produced nanoparticles were characterized using X-ray diffraction (XRD) and electrochem. investigations. According to XRD measurements, the synthesized NPs were cryst. in nature, with crystallite sizes of about 2 nm. The electrochem. properties of the synthesized NPs were studied in alk. soln. through a rotating ring-disk electrode (RRDE) technique of cyclic voltammetry. The PdNi nanoparticles supported on carbon (PdNi/C) were used as electrocatalysts and their activity and stability were compared with the homemade Pd/C and Pt/C. In alk. soln., PdNi/C electrocatalysts showed improved oxygen redn. catalytic activity over benchmark Pd/C and Pt/C electrocatalysts in all compn. ratios. Furthermore, stability expts. revealed that PdNi 50:50 is more stable in alk. soln. than pure Pd and other PdNi compns.
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    Wang, L.; Dong, K. J.; Wang, C. C.; Zou, R. P.; Zhou, Z. Y.; Yu, A. B. Computer Simulation of the Packing of Nanoparticles. Powder Technol. 2022, 401, 117317,  DOI: 10.1016/j.powtec.2022.117317
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    Computer simulation of the packing of nanoparticles
    Wang, L.; Dong, K. J.; Wang, C. C.; Zou, R. P.; Zhou, Z. Y.; Yu, A. B.
    Powder Technology (2022), 401 (), 117317CODEN: POTEBX; ISSN:0032-5910. (Elsevier B.V.)
    The packing of nanoparticles down to 20 nm is simulated by the discrete element method (DEM). The model is validated by good agreement between the simulated and measured porosity. It is found that the previous relationship between porosity and the force ratio of cohesion to gravity can also be applied to the packing of nanoparticles. However, different from microparticles, nanoparticle packing begins with agglomeration and then the agglomerates are packed together. The resulting packing structure is thus more like chains of agglomerates. The agglomeration process becomes more dominant when particle size decreases. Due to agglomeration, the packing structure of nanoparticles is found to be more sensitive to the initial porosity than that of microparticles, and the effects are analyzed in terms of the temporal evolution of agglomerates. The fractal anal. indicates that the agglomerates are fractal-like while the whole packing is not fractal-like. The packing structure can be characterized by the radial distribution function and coordination no. The results indicate that for nanoparticles, with decreasing particle size, local packing structure becomes denser although the overall porosity increases, which is different from that of microparticles. The results link the packing of particles at different scales, from macro to nano, while also reveal the crit. difference between the packing of nanoparticles and that of other particles.
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    Eldridge, M. D.; Madden, P. A.; Frenkel, D. Entropy-Driven Formation of a Superlattice in a Hard-Sphere Binary Mixture. Nature 1993, 365 (6441), 35– 37,  DOI: 10.1038/365035a0
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    Entropy-driven formation of a superlattice in a hard-sphere binary mixture
    Eldridge, M. D.; Madden, P. A.; Frenkel, D.
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    The possibility that the formation of an AB13 superlattice might be supported by entropy effects alone was investigated by computer simulations of a binary mixt. of hard spheres. Calcns. show that entropy alone is sufficient to stabilize the AB13 phase. and that the full phase diagram of this system is surprisingly complex. The results also suggest that vitrification or slow crystal nucleation in exptl. studies of colloidal hard spheres can prevent the formation of equil. phases.
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    Wang, Z.; Schliehe, C.; Bian, K.; Dale, D.; Bassett, W. A.; Hanrath, T.; Klinke, C.; Weller, H. Correlating Superlattice Polymorphs to Internanoparticle Distance, Packing Density, and Surface Lattice in Assemblies of PbS Nanoparticles. Nano Lett. 2013, 13 (3), 1303– 1311,  DOI: 10.1021/nl400084k
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    Correlating Superlattice Polymorphs to Internanoparticle Distance, Packing Density, and Surface Lattice in Assemblies of PbS Nanoparticles
    Wang, Zhongwu; Schliehe, Constanze; Bian, Kaifu; Dale, Darren; Bassett, William A.; Hanrath, Tobias; Klinke, Christian; Weller, Horst
    Nano Letters (2013), 13 (3), 1303-1311CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)
    Assemblies of 3.5 nm PbS nanoparticles (NPs) nucleate in three dominant superlattice polymorphs: amorphous, bcc. and fcc. phase. This superlattice relation can be controlled by the inter-NP distance without changing the NP size. Upon increase of inter-NP distance, the packing d. decreases, and the capping mols. at NP surfaces change in structure and accordingly modify the surface energy. The driving force for NP assembly develops from an entropic maximization to a redn. of total free energy through multiple interactions between surface mols. and NPs and resulting variation of surface mols. Upon long-term aging and addnl. thermal treatment, fcc. undergoes a tetragonal distortion and subsequently transforms to bcc. phase, and simultaneously, the NPs embedded in supercrystals reduce surface energy primarily in {200} facets. Linking mol.-NP interactions with changes of packing d. and surface lattice spacings of NPs allows for an interpretation of principles governing the nucleation, structure stability, and transformation of PbS NP-assembled supercrystals.
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    Bouju, X.; Duguet, É.; Gauffre, F.; Henry, C. R.; Kahn, M. L.; Mélinon, P.; Ravaine, S. Nonisotropic Self-Assembly of Nanoparticles: From Compact Packing to Functional Aggregates. Adv. Mater. 2018, 30 (27), 1706558,  DOI: 10.1002/adma.201706558
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    Wang, L.; Lavacchi, A.; Bellini, M.; D’Acapito, F.; Benedetto, F. D.; Innocenti, M.; Miller, H. A.; Montegrossi, G.; Zafferoni, C.; Vizza, F. Deactivation of Palladium Electrocatalysts for Alcohols Oxidation in Basic Electrolytes. Electrochim. Acta 2015, 177, 100– 106,  DOI: 10.1016/j.electacta.2015.02.026
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    Deactivation of Palladium Electrocatalysts for Alcohols Oxidation in Basic Electrolytes
    Wang, Lianqin; Lavacchi, Alessandro; Bellini, Marco; D'Acapito, Francesco; Benedetto, Francesco Di; Innocenti, Massimo; Miller, Hamish A.; Montegrossi, Giordano; Zafferoni, Claudio; Vizza, Francesco
    Electrochimica Acta (2015), 177 (), 100-106CODEN: ELCAAV; ISSN:0013-4686. (Elsevier Ltd.)
    Deactivation is one the main causes still preventing the full exploitation of Pd electrocatalysts in alk. direct alc. fuel cells and the electrochem. reforming of alcs. While often attributed to the adsorption of poisoning species generated in the alcs. oxidn., deactivation is provoked by the formation of Pd oxides. A combined approach including (i) fuel cell runs, (ii) cyclic voltammetry and (iii) near edge x-ray absorption spectroscopy has enabled the authors to draw the conclusions reported.
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    Oliveira, V. L.; Morais, C.; Servat, K.; Napporn, T. W.; Tremiliosi-Filho, G.; Kokoh, K. B. Glycerol Oxidation on Nickel Based Nanocatalysts in Alkaline Medium - Identification of the Reaction Products. J. Electroanal. Chem. 2013, 703, 56,  DOI: 10.1016/j.jelechem.2013.05.021
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    Glycerol oxidation on nickel based nanocatalysts in alkaline medium - Identification of the reaction products
    Oliveira, V. L.; Morais, C.; Servat, K.; Napporn, T. W.; Tremiliosi-Filho, G.; Kokoh, K. B.
    Journal of Electroanalytical Chemistry (2013), 703 (), 56-62CODEN: JECHES; ISSN:1873-2569. (Elsevier B.V.)
    Carbon-supported Ni-based nanoparticles were prepd. by the impregnation method and used as anode electrocatalysts for glycerol conversion. These metallic powders were mixed with a suitable amt. of a Nafion/water soln. to make catalytic inks which were then deposited onto the surface of C Toray used as a conductive substrate. Long-term electrolyzes of glycerol were carried out in alk. medium by chronoamperometry expts. Anal. of the oxidn. products was performed with ion-exclusion liq. chromatog. which separates the analytes by ascending pKa. The spectroscopic measurements showed that the Co content in the anode compn. did contribute to the CC bond cleavage of the initial mol. of glycerol.
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    Goetz, M. K.; Bender, M. T.; Choi, K.-S. Predictive Control of Selective Secondary Alcohol Oxidation of Glycerol on NiOOH. Nat. Commun. 2022, 13 (1), 5848,  DOI: 10.1038/s41467-022-33637-7
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    Predictive control of selective secondary alcohol oxidation of glycerol on NiOOH
    Goetz, McKenna K.; Bender, Michael T.; Choi, Kyoung-Shin
    Nature Communications (2022), 13 (1), 5848CODEN: NCAOBW; ISSN:2041-1723. (Nature Portfolio)
    Many biomass intermediates are polyols and selectively oxidizing only a primary or secondary alc. group is beneficial for the valorization of these intermediates. For example, prodn. of 1,3-dihydroxyacetone, a highly valuable oxidn. product of glycerol, requires selective secondary alc. oxidn. However, selective secondary alc. oxidn. is challenging due to its steric disadvantage. This study demonstrates that NiOOH, which oxidizes alcs. via two dehydrogenation mechanisms, hydrogen atom transfer and hydride transfer, can convert glycerol to 1,3-dihydroxyacetone with high selectivity when the conditions are controlled to promote hydrogen atom transfer, favoring secondary alc. oxidn. This rational prodn. of 1,3-dihydroxyacetone achieved by selectively enabling one desired dehydrogenation pathway, without requiring alteration of catalyst compn., demonstrates how comprehensive mechanistic understanding can enable predictive control over selectivity.
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    Zhang, N.; Wang, J.; Zhang, W.; Zhao, Y.; Dong, Z.; Wu, Z.; Xu, G.-R.; Wang, L. Self-Supported PdNi Dendrite on Ni Foam for Improving Monohydric Alcohol and Polyhydric Alcohols Electrooxidation. Fuel 2022, 326, 125083,  DOI: 10.1016/j.fuel.2022.125083
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    Self-supported PdNi dendrite on Ni foam for improving monohydric alcohol and polyhydric alcohols electrooxidation
    Zhang, Ning; Wang, Jing; Zhang, Wen; Zhao, Yingxiu; Dong, Zemeng; Wu, Zexing; Xu, Guang-Rui; Wang, Lei
    Fuel (2022), 326 (), 125083CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    Despite considerable efforts to study direct alc. fuel cells (DAFCs), the development of efficient bifunctional catalysts for monohydric alc. and polyhydric alcs. remains a great challenge. This work reports the prepn. of self-supported PdNi dendrites on Ni foam (self-supported PdNi DNTs/NF) with a large sp. surface area by a simple self-sacrificing template and hydrothermal method. The presence of NF with enrichment of nucleation sites is crucial for the generation of self-supported PdNi DNTs. The as-obtained self-supported PdNi DNTs/NF exhibits an excellent property for ethanol and glycerol electrooxidn. with the mass activity of 2375.7 mA mg-1cat and 2451.6 mA mg-1cat, the specific activity of 10.07 mA cm-2 and 10.84 mA cm-2, resp., in alk. media, which should attribute to abundant high-index facets and low-coordinated atoms on the edge of branches. Furthermore, the PdNi DNTs/NF exhibits outstanding long-term durability in the current-time test for 7200 s with superior anti-CO poisoning performance, possessing a potential application in DAFCs.
  65. 65
    Luo, H.; Yukuhiro, V. Y.; Fernández, P. S.; Feng, J.; Thompson, P.; Rao, R. R.; Cai, R.; Favero, S.; Haigh, S. J.; Durrant, J. R.; Stephens, I. E. L.; Titirici, M.-M. Role of Ni in PtNi Bimetallic Electrocatalysts for Hydrogen and Value-Added Chemicals Coproduction via Glycerol Electrooxidation. ACS Catal. 2022, 12 (23), 14492– 14506,  DOI: 10.1021/acscatal.2c03907
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    65
    Role of nickel in platinum nickel bimetallic electrocatalysts for hydrogen and value-added chemicals coproduction through glycerol electrooxidation
    Luo, Hui; Yukuhiro, Victor Y.; Fernandez, Pablo S.; Feng, Jingyu; Thompson, Paul; Rao, Reshma R.; Cai, Rongsheng; Favero, Silvia; Haigh, Sarah J.; Durrant, James R.; Stephens, Ifan E. L.; Titirici, Maria-Magdalena
    ACS Catalysis (2022), 12 (23), 14492-14506CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
    Pt-based bimetallic electrocatalysts are promising candidates to convert surplus glycerol from the biodiesel industry to value-added chems. and coproduce hydrogen. It is expected that the nature and content of the elements in the bimetallic catalyst can not only affect the reaction kinetics but also influence the product selectivity, providing a way to increase the yield of the desired products. Hence, in this work, we investigate the electrochem. oxidn. of glycerol on a series of PtNi nanoparticles with increasing Ni content using a combination of physicochem. structural anal., electrochem. measurements, operando spectroscopic techniques, and advanced product characterizations. With a moderate Ni content and a homogenously alloyed bimetallic Pt-Ni structure, the PtNi2 catalyst displayed the highest reaction activity among all materials studied in this work. In situ FTIR data show that PtNi2 can activate the glycerol mol. at a more neg. potential (0.4 VRHE) than the other PtNi catalysts. In addn., its surface can effectively catalyze the complete C-C bond cleavage, resulting in lower CO poisoning and higher stability. Operando X-ray absorption spectroscopy and UV-vis spectroscopy suggest that glycerol adsorbs strongly onto surface Ni(OH)x sites, preventing their oxidn. and activation of oxygen or hydroxyl from water. As such, we propose that the role of Ni in PtNi toward glycerol oxidn. is to tailor the electronic structure of the pure Pt sites rather than a bifunctional mechanism. Our expts. provide guidance for the development of bimetallic catalysts toward highly efficient, selective, and stable glycerol oxidn. reactions.
  66. 66
    Mphahlele, N. E.; Ipadeola, A. K.; Haruna, A. B.; Mwonga, P. V.; Modibedi, R. M.; Palaniyandy, N.; Billing, C.; Ozoemena, K. I. Microwave-induced Defective PdFe/C Nano-electrocatalyst for Highly Efficient Alkaline Glycerol Oxidation Reactions. Electrochim. Acta 2022, 409, 139977,  DOI: 10.1016/j.electacta.2022.139977
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    66
    Microwave-induced defective PdFe/C nano-electrocatalyst for highly efficient alkaline glycerol oxidation reactions
    Mphahlele, Nonhlanhla Eugenia; Ipadeola, Adewale Kabir; Haruna, Aderemi Bashiru; Mwonga, Patrick Vaati; Modibedi, Remegia Mmalewane; Palaniyandy, Nithyadharseni; Billing, Caren; Ozoemena, Kenneth Ikechukwu
    Electrochimica Acta (2022), 409 (), 139977CODEN: ELCAAV; ISSN:0013-4686. (Elsevier Ltd.)
    Pd-based mono- and bi-metallic nano-electrocatalysts (Pd/C and PdFe/C) have been synthesized using two different methods for comparison: conventional sodium borohydride (NaBH4) route and microwave-assisted redn. process. The performance of the nano-electrocatalysts is tested for glycerol oxidn. reaction (GlyOR) in an alk. medium. DFT simulation proves that incorporation of Fe to Pd(111) leads to an increased partial d. of states (PDOS) compared to Pd alone, confirming the importance for bimetallic nano-electrocatalyst. The adsorption energy of glycerol onto PdFe is slightly weaker (A.E. = -48.89 eV) than the Pd alone (A.E. = -48.60 eV), indicating the ease with which glycerol can be generated at the PdFe surface than at the Pd alone. XRD show that microwave-irradiated samples (Pd(MW) and PdFe(MW)) are more cryst. than the conventional Pd and PdFe. TEM images show that the Pd(MW) and PdFe(MW) have slightly larger particle sizes (5.30 - 7.40 nm) than those from the conventional route (2.48 - 3.02 nm). Nitrogen adsorption-desorption anal. shows that the microwave samples exhibit slightly larger surface area compared to samples from NaBH4 route. Raman and XPS show that Pd(MW) and PdFe(MW) are more prone to defects (i.e., oxygen vacancies) compared to the NaBH4 route. The microwave samples gave the highest electrocatalytic properties toward glycerol than the NaBH4 route (including high electrochem. active surface area, high c.d. response, high resistance to poisoning due to carbonaceous intermediates arising from the GlyOR, and high cond. or low interfacial resistance) compared to samples from the conventional NaBH4 method. The findings in this work go a long way to understanding the physico-chem. and electrochem. effects of microwave irradn. on bimetallic electrocatalyst for glycerol oxidn. reaction, which open new opportunities for developing high-performance direct alk. glycerol fuel cells.
  67. 67
    Houache, M. S. E.; Shubair, A.; Sandoval, M. G.; Safari, R.; Botton, G. A.; Jasen, P. V.; González, E. A.; Baranova, E. A. Influence of Pd and Au on Electrochemical Valorization of Glycerol over Ni-Rich Surfaces. J. Catal. 2021, 396, 1– 13,  DOI: 10.1016/j.jcat.2021.02.008
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    Influence of Pd and Au on electrochemical valorization of glycerol over Ni-rich surfaces
    Houache, Mohamed S. E.; Shubair, Asma; Sandoval, Mario G.; Safari, Reza; Botton, Gianluigi A.; Jasen, Paula V.; Gonzalez, Estela A.; Baranova, Elena A.
    Journal of Catalysis (2021), 396 (), 1-13CODEN: JCTLA5; ISSN:0021-9517. (Elsevier Inc.)
    Herein the authors synthesized bi-metallic Pd@Ni and Au@Ni core-shell-like nanoparticles (NPs) for glycerol electrooxidn. reaction (GEOR) in alk. media. The morphol., structural and surface properties of the NPs were evaluated using a range of physicochem. techniques. The catalytic activity and stability were studied using the three-electrode electrochem. cell and 25 cm2- continuous electrolysis cell. Among different at. ratios, Ni80Pd20 and Ni90Au10 nanoparticles showed the highest current densities which are ∼4.5 and 4.2 times higher than spherical Ni, resp. The addn. of Pd and Au (<20 at.%) to Ni nanoparticles led to a remarkable glycerate selectivity of ∼73.1% and 65.7% for Ni80Pd20 and Ni90Au10 catalysts at 1.3 V and 50°, resp. Notably, after 6 h of electrolysis Pd@Ni and Au@Ni tend to suppress the C-C bond cleavage, compared to Ni at any applied potentials and temps. The DFT calcns. predicted that the addn. of Pd or Au to Ni reduces the work function of M@Ni NPs, which strengthens the OH adsorption and enhances the removal of GEOR intermediates.
  68. 68
    Wang, H.; Thia, L.; Li, N.; Ge, X.; Liu, Z.; Wang, X. Pd Nanoparticles on Carbon Nitride-Graphene for the Selective Electro-Oxidation of Glycerol in Alkaline Solution. ACS Catal. 2015, 5 (6), 3174– 3180,  DOI: 10.1021/acscatal.5b00183
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    Pd Nanoparticles on Carbon Nitride-Graphene for the Selective Electro-Oxidation of Glycerol in Alkaline Solution
    Wang, Haibo; Thia, Larissa; Li, Nan; Ge, Xiaoming; Liu, Zhaolin; Wang, Xin
    ACS Catalysis (2015), 5 (6), 3174-3180CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
    A hybrid support consisting of C nitride and graphene (CNx/G) was prepd. by annealing polypyrrole/GO at 800°. Pd nanoparticles (NPs) are then loaded onto the support by a microwave-polyol method. Pd-CNx/G was used as a catalyst for glycerol electrooxidn. in 0.5 M NaOH aq. soln. Electrochem. characterization and product anal. by HPLC show that, in comparison to Pd NPs supported on C black, Pd NPs on a support contg. N atoms has the ability to promote selectivity toward C3 products as well as increase activity. The main factors influencing the selectivity and activity are also discussed.
  69. 69
    Melle, G.; de Souza, M. B. C.; Santiago, P. V. B.; Corradini, P. G.; Mascaro, L. H.; Fernández, P. S.; Sitta, E. Glycerol Electro-Oxidation at Pt in Alkaline Media: Influence of Mass Transport and Cations. Electrochim. Acta 2021, 398, 139318,  DOI: 10.1016/j.electacta.2021.139318
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    Glycerol electro-oxidation at Pt in alkaline media: influence of mass transport and cations
    Melle, Gabriel; de Souza, Matheus B. C.; Santiago, Patricia V. B.; Corradini, Patricia Gon; Mascaro, Lucia Helena; Fernandez, Pablo S.; Sitta, Elton
    Electrochimica Acta (2021), 398 (), 139318CODEN: ELCAAV; ISSN:0013-4686. (Elsevier Ltd.)
    Glycerol is an important biomass-derived product with potential to be applied on energy converting systems or as platform mol. in electrosynthesis. In this work we studied the glycerol oxidn. reaction (GOR) in alk. media contg. distinct alk. cations and controlling the mass transport. The cyclic voltammograms were deconvoluted into three processes and the changes in the charge of each process revealed that mass transport affects the GOR in a complex matter, depending on both applied potential and electrolyte cation. Regardless of the cation on supporting electrolyte, high-performance liq. chromatog. (HPLC) anal. revealed the prodn. of glycerate and lactate during GOR. Finally, potential oscillations under current control were mapped, highlighting the influence of both cations and mass transport, even in the systems with very similar behavior under potential control.
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    Zhou, Y.; Shen, Y.; Piao, J. Sustainable Conversion of Glycerol into Value-Added Chemicals by Selective Electro-Oxidation on Pt-Based Catalysts. ChemElectroChem 2018, 5 (13), 1636– 1643,  DOI: 10.1002/celc.201800309
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    Sustainable Conversion of Glycerol into Value-Added Chemicals by Selective Electro-Oxidation on Pt-Based Catalysts
    Zhou, Yongfang; Shen, Yi; Piao, Jinhua
    ChemElectroChem (2018), 5 (13), 1636-1643CODEN: CHEMRA; ISSN:2196-0216. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Electro-oxidn. of glycerol affords a totally green route to produce high value-added chems. Herein, we report a study on glycerol electro-oxidn. over a series of graphene nanosheet supported Pt (Pt/GNS), PtNi (PtNi/GNS), PtRu (PtRu/GNS), PtRh (PtRh/GNS), PtRuNi (PtRuNi/GNS), and PtRhNi (PtRhNi/GNS) catalysts in alk. soln. The activity of the catalysts was evaluated by cyclic voltammetry, linear sweep voltammetry, and chronoamperometric measurements. The PtRh/GNS and PtRhNi/GNS catalysts exhibited superior activity in terms of higher current densities and lower onset potentials. The products of glycerol oxidn. formed at potentials of -0.4, -0.1, and 0.2 V, were systematically analyzed by high performance liq. chromatog. (HPLC). Five compds. as products from glycerol electro-oxidn. catalyzed by the prepd. materials were found, including glyceraldehyde, glycolic acid, tartronic acid, glyceric acid and oxalate acid. The product distribution at the different potentials was investigated for all catalysts. A max. glycolic acid selectivity of 65.4 % was obtained for the Pt/GNS catalyst at 0.2 V while a max. glyceric acid selectivity of 47.7 % was achieved using the PtNi/GNS catalyst at -0.1 V. It was found that the introduction of Ru facilitated the formation of C3 products while the addn. of Rh was beneficial for the formation of C2 products. Based on HPLC results, the pathways of glycerol electro-oxidn. by the prepd. catalysts were proposed.
  71. 71
    Valter, M.; dos Santos, E. C.; Pettersson, L. G. M.; Hellman, A. Partial Electrooxidation of Glycerol on Close-Packed Transition Metal Surfaces: Insights from First-Principles Calculations. J. Phys. Chem. C 2020, 124 (33), 17907– 17915,  DOI: 10.1021/acs.jpcc.0c04002
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    Partial Electrooxidation of Glycerol on Close-Packed Transition Metal Surfaces: Insights from First-Principles Calculations
    Valter, Mikael; dos Santos, Egon Campos; Pettersson, Lars G. M.; Hellman, Anders
    Journal of Physical Chemistry C (2020), 124 (33), 17907-17915CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    Glycerol is a byproduct of biodiesel prodn. and an abundant feedstock for the synthesis of high-value chems. One promising approach for valorization of glycerol is electrooxidn. yielding H and value-added products. However, due to the vast amt. of intermediary steps and possible products, the process is not fully understood. Here, the 1st two deprotonations of glycerol on close-packed transition metals (Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, and Au) were studied using d. functional theory calcns. together with the computational H electrode. The theor. limiting potential for the studied reaction is ∼0 V vs. the reversible H electrode, ranging from -0.12 V for Ru to +0.35 V for Au. Also, Ru, Rh, Ir, Ag, and Au are selective toward dihydroxyacetone and its derivs., while Pd and Pt are selective toward either dihydroxyacetone or glyceraldehyde and their derivs., and that Cu, Co, and Ni are selective toward hydropyruvic acid. The results can be rationalized in terms of the relative bond strengths of C and O on the metal. Solvent effects are generally small, the exceptions being the limiting potential on Cu and the mechanism on Rh. These results can be used to steer the selectivity toward more valuable products and thereby increase the economic yield of biodiesel prodn.
  72. 72
    Valter, M.; Santos, E. C.; Pettersson, L. G. M.; Hellman, A. Selectivity of the First Two Glycerol Dehydrogenation Steps Determined Using Scaling Relationships. ACS Catal. 2021, 11 (6), 3487– 3497,  DOI: 10.1021/acscatal.0c04186
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    Selectivity of the First Two Glycerol Dehydrogenation Steps Determined Using Scaling Relationships
    Valter, Mikael; Santos, Egon Campos dos; Pettersson, Lars G. M.; Hellman, Anders
    ACS Catalysis (2021), 11 (6), 3487-3497CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
    Glycerol is a byproduct of biodiesel prodn. and an abundant feedstock that can be used for the synthesis of high-value chems. There are many approaches for glycerol valorization, but, due to the complicated reaction mechanism, controlling which products are produced is challenging. Here, we describe glycerol's chem. selectivity for different metallic catalysts using descriptors for carbon (mainly *C, *CH2OH) and oxygen (mainly *O, CH3O*). The quality of these descriptors and the weighted combinations thereof are validated based on their fit, via linear regression, to the binding energies of all reaction intermediates generated in the first two glycerol dehydrogenation steps on a no. of close-packed Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, and Au surfaces. We show that *CH2OH is a better descriptor than *C for the studied carbon-bound intermediates, which is attributed to the observation that the adjacent *OH group interacts with the surface. This leads to a neg. oxygen dependence, which can be generalized to similar alc.-derived adsorbates. Furthermore, we show that CH3O* is a better oxygen descriptor than *O for the studied intermediates. This is mainly attributed to the difference between the single and double bonds, as we show that *OH is closer to the accuracy of CH3O*. Multilinear regression with different combinations of *C, *O, and *OH is comparable in accuracy to that of *CH2OH and CH3O*. Scaling relationships are used to det. the selectivity map for glycerol dehydrogenation. The results show that the first dehydrogenation is selective toward two different intermediates (one bonded via the secondary carbon and the other via the secondary oxygen) depending on the relative bond strength of the carbon and oxygen descriptors. The second dehydrogenation step results in five intermediates, again depending primarily on the relative bond strength of carbon and oxygen to the surface. The selectivity maps can be used together with kinetic considerations and exptl. data to find catalyst candidates for glycerol dehydrogenation.
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    Yu, X.; dos Santos, E. C.; White, J.; Salazar-Alvarez, G.; Pettersson, L. G. M.; Cornell, A.; Johnsson, M. Electrocatalytic Glycerol Oxidation with Concurrent Hydrogen Evolution Utilizing an Efficient MoOx/Pt Catalyst. Small 2021, 17 (44), 2104288,  DOI: 10.1002/smll.202104288
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    Electrocatalytic Glycerol Oxidation with Concurrent Hydrogen Evolution Utilizing an Efficient MoOx/Pt Catalyst
    Yu, Xiaowen; dos Santos, Egon Campos; White, Jai; Salazar-Alvarez, German; Pettersson, Lars G. M.; Cornell, Ann; Johnsson, Mats
    Small (2021), 17 (44), 2104288CODEN: SMALBC; ISSN:1613-6810. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Glycerol electrolysis affords a green and energetically favorable route for the prodn. of value-added chems. at the anode and H2 prodn. in parallel at the cathode. Here, a facile method for trapping Pt nanoparticles at oxygen vacancies of molybdenum oxide (MoOx) nanosheets, yielding a high-performance MoOx/Pt composite electrocatalyst for both the glycerol oxidn. reaction (GOR) and the hydrogen evolution reaction (HER) in alk. electrolytes, is reported. Combined electrochem. expts. and theor. calcns. reveal the important role of MoOx nanosheets for the adsorption of glycerol mols. in GOR and the dissocn. of water mols. in HER, as well as the strong electronic interaction with Pt. The MoOx/Pt composite thus significantly enhances the specific mass activity of Pt and the kinetics for both reactions. With MoOx/Pt electrodes serving as both cathode and anode, two-electrode glycerol electrolysis is achieved at a cell voltage of 0.70 V to reach a c.d. of 10 mA cm-2, which is 0.90 V less than that required for water electrolysis.
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    Yaylayan, V.; Harty-Majors, S.; Ismail, A. Investigation of Dl-Glyceraldehyde-Dihydroxyacetone Interconversion by FTIR Spectroscopy. Carbohydr. Res. 1999, 318 (1–4), 20– 25,  DOI: 10.1016/S0008-6215(99)00077-4
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    Investigation of DL-glyceraldehyde-dihydroxyacetone interconversion by FTIR spectroscopy
    Yaylayan, V. A.; Harty-Majors, S.; Ismail, A. A.
    Carbohydrate Research (1999), 318 (1-4), 20-25CODEN: CRBRAT; ISSN:0008-6215. (Elsevier Science Ltd.)
    Interconversion of dihydroxyacetone and DL-glyceraldehyde was studied in different solvents and temps. by FTIR spectroscopy. Dissoln. in water or triethylamine, and increasing temps. caused the dissocn. of the dimeric forms of both compds. into monomers and subsequently inter-conversion of dihydroxyacetone and DL-glyceraldehyde. Dioxane, on the other hand, did not initiate such inter-conversions. FTIR anal. in different solvents has also indicated that monomeric DL-glyceraldehyde can exist in two distinct intramolecularly H-bonded forms. A five-membered ring form was predominant in aq. solns. of the dissocd. DL-glyceraldehyde dimer, whereas a six-membered ring form was preferred in triethylamine soln. or in aq. soln. of dissocd. dihydroxyacetone dimer. However, in aq. solns. of DL-glyceraldehyde dimer, the five-membered ring conformation was slowly transformed into the six-membered ring form under slightly basic pH. In addn., dihydroxyacetone predominantly converted into the six-membered H-bonded conformation of glyceraldehyde when dissolved in water. This was attributed to the preferential formation of the trans- or E-enediol as an intermediate. Temp.-dependent spectra have also indicated that increasing the temp. favored the formation of glyceraldehyde in the aq. equil. mixts. of dimeric DL-glyceraldehyde and dihydroxyacetone.
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    Rasrendra, C. B.; Fachri, B. A.; Makertihartha, I. G. B. N.; Adisasmito, S.; Heeres, H. J. Catalytic Conversion of Dihydroxyacetone to Lactic Acid Using Metal Salts in Water. ChemSusChem 2011, 4 (6), 768– 777,  DOI: 10.1002/cssc.201000457
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    We herein present a study on the application of homogeneous catalysts in the form of metal salts on the conversion of trioses, such as dihydroxyacetone (DHA), and glyceraldehyde (GLY) to lactic acid (LA) in water. A wide range of metal salts (26 in total) were examd. AlIII salts were identified as the most promising and essentially quant. LA yields (>90 mol %) were obtained at 140 °C and a reaction time of 90 min. A reaction pathway is proposed and a kinetic model using the power law approach was developed for the conversion of DHA to LA with pyruvaldehyde (PRV) as the intermediate. Good agreement between exptl. data and the model was obtained. Model predictions, supported by expts., indicate that a high yield of LA is favored in dil. solns. of DHA (0.1 M) at elevated temps. (180 °C) and reaction times less than 10 min.
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    Kinetics of mutual isomerization of trioses and their dehydration to methyl glyoxal
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  1. Irina Terekhina, Mats Johnsson. Improving Glycerol Electrooxidation Performance on Nanocubic PtCo Catalysts. ACS Applied Materials & Interfaces 2024, 16 (42) , 56987-56996. https://doi.org/10.1021/acsami.4c10219
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  3. Junhao Wu, Xiao Zhang, Sijia Ren, Xinhui Lu, Jiaxin Yang, Kui Li. Employing a MoO 2 @NiO heterojunction as a highly selective and efficient electrochemical ethanol-to-acetaldehyde conversion catalyst. CrystEngComm 2024, 26 (47) , 6701-6706. https://doi.org/10.1039/D4CE01039F
  4. Yang Zhang, Lin Wang, Shengmin Pan, Lin Zhou, Man Zhang, Yaoyue Yang, Wenbin Cai. Improving the Electrochemical Glycerol-to-Glycerate Conversion at Pd Sites via the Interfacial Hydroxyl Immigrated from Ni Sites. Molecules 2024, 29 (16) , 3890. https://doi.org/10.3390/molecules29163890
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  • Abstract

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    Scheme 1

    Scheme 1. Schematic Representation of the Pd and PdNi Nanoparticle Synthesis
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    Figure 1

    Figure 1. TEM and HRTEM images of (a,b) Pd NPs and (c,d) PdNi NPs. The insets of images (a,b) show particle size distributions of the corresponding catalysts. (e) PXRD patterns of Pd and PdNi NPs.

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    Figure 2

    Figure 2. (a) CV in 1.0 M NaOH for Pd/C and PdNi/C. (b) LSV in 1.0 M NaOH and 0.50 M Gly for Pd/C and PdNi/C along with the CV from (a). (c) LSV from (b) normalized by ECSA. (d) LSV from (b) normalized by the mass of Pd in the Pd/C and PdNi/C catalysts. All sweeps were conducted at 25 °C and a sweep rate of 50 mV s–1.

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    Figure 3

    Figure 3. ICPCs for PdNi/C at 40 °C in a supporting electrolyte of 1.0 M NaOH with Gly concentrations of 0.10 M (blue triangles) and 0.50 M (red circles). (a) No normalization, i.e., current; (b) specific activity, i.e., normalized by ECSA; and (c) mass activity, i.e., normalized by the mass of Pd in the PdNi/C catalyst.

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    Figure 4

    Figure 4. ICPCs for Pd/C (black squares) and PdNi/C (red circles) at 40 °C in a 1.0 M NaOH and 0.50 M Gly solution. (a) No normalization, i.e., current; (b) specific activity, i.e., normalized by ECSA; and (c) mass activity, i.e., normalized by the mass of Pd in the Pd/C and PdNi/C catalysts.

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    Figure 5

    Figure 5. Product fractions analyzed by HPLC for (a) PdNi/C and (b) Pd/C catalysts at varying potentials.

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    Figure 6

    Figure 6. Representation of the calculated Gly electrooxidation pathway of Pd(111) and PdNi(111) catalysts in alkaline solution with PDS values (in eV) of each oxidation step. The oxidation pathway of each intermediate is shown using different colors as follows: (1) Gly–DHA (black), (1′) DHA–HPA (black), (2) Gly–GD (blue), (2′) GD–GLA (blue), (3) GLA–GA (red), (3′) GA–FA (red), (4) GLA–TTA (magenta), (4′) TTA–MLA (magenta), (5) GA–OA (gray), and (6) DHA–LA (green). Here, PDS represents the minimum potential required to overcome the energy barrier of the reactions illustrated in Figures S5–S10.

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  • References

    This article references 77 other publications.

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      Mahlia, T. M. I.; Syazmi, Z. A. H. S.; Mofijur, M.; Abas, A. P.; Bilad, M. R.; Ong, H. C.; Silitonga, A. S. Patent Landscape Review on Biodiesel Production: Technology Updates. Renewable Sustainable Energy Rev. 2020, 118, 109526,  DOI: 10.1016/j.rser.2019.109526
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      Patent landscape review on biodiesel production: Technology updates
      Mahlia, T. M. I.; Syazmi, Z. A. H. S.; Mofijur, M.; Abas, A. E. Pg; Bilad, M. R.; Ong, Hwai Chyuan; Silitonga, A. S.
      Renewable & Sustainable Energy Reviews (2020), 118 (), 109526CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
      A review. Biodiesel is a renewable fuel made from vegetable oils and animal fats. Compared with fossil fuels, it has the potential to alleviate environmental pressures and achieve sustainable development. In this paper, 1660 patents related to biodiesel prodn. were reviewed. They were published between Jan. 1999 and July 2018 and were retrieved from the Derwent Innovation patent database. The patents were grouped into five categories depending on whether they related to starting materials, pre-treatment methods, catalysts, reactors and processing methods, or testing methods. Their anal. shows that the availability of biodiesel starting materials depends on climate, geog. location, local soil conditions, and local agricultural practices. Starting materials constitute 75% of overall prodn. costs and, therefore, it is crucial to select the best feedstock. Pre-treatment of feedstock can improve its suitability for processing and increase extn. effectiveness and oil yield. Catalysts can enhance the soly. of alc., leading to higher reaction rates, faster biodiesel prodn. processes, and lower biodiesel prodn. costs. Moreover, the app. and processes used strongly affect the oil yield and quality, and prodn. cost. In order to be commercialized and marketed, biodiesel should pass either the American Society for Testing and Materials (ASTM) stds. or European Stds. (EN). Due to increases in environmental awareness, it is likely that the no. of published patents on biodiesel prodn. will remain stable or even increase.
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      Likhanov, V. A.; Lopatin, O. P. Research of High-Speed Diesel Engines of Small Dimension on Biofuel. J. Phys.: Conf. Ser. 2019, 1399 (5), 055016,  DOI: 10.1088/1742-6596/1399/5/055016
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      Research of high-speed diesel engines of small dimension on biofuel
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      Journal of Physics: Conference Series (2019), 1399 (International Scientific Conference "Conference on Applied Physics, Information Technologies and Engineering-APITECH-2019"), 055016CODEN: JPCSDZ; ISSN:1742-6588. (IOP Publishing Ltd.)
      The paper substantiates the need for the use of biofuels in diesel engines. It is shown that the choice for diesel alternative biofuel with a perspective should be carried out in accordance with the design features of the engine and during its primary tests. The paper studies such eco-friendly energy sources as methanol, ethanol and Me ether of rapeseed oil. Methanol, ethanol and Me ester of rapeseed oil potentially lead to some solns. to environmental problems, as for their prodn., there are quite abundant resources and these energy sources are characterized by relatively low emissions of harmful substances when burning. The ways of bioethanol prodn. from various raw materials and the process of rapeseed oil methanolysis are considered. Exptl. studies of biodiesel operating on alc.-fuel emulsions, methanol and Me ether of rapeseed oil were carried out.
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      Biodiesel: From Production to Combustion; Tabatabaei, M., Aghbashlo, M., Eds.; Biofuel and Biorefinery Technologies; Springer International Publishing: Cham, 2019; Vol. 8. DOI: 10.1007/978-3-030-00985-4 .
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      Ciriminna, R.; Pina, C. D.; Rossi, M.; Pagliaro, M. Understanding the Glycerol Market. Eur. J. Lipid Sci. Technol. 2014, 116 (10), 1432– 1439,  DOI: 10.1002/ejlt.201400229
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      Understanding the glycerol market
      Ciriminna, Rosaria; Pina, Cristina Della; Rossi, Michele; Pagliaro, Mario
      European Journal of Lipid Science and Technology (2014), 116 (10), 1432-1439CODEN: EJLTFM; ISSN:1438-7697. (Wiley-VCH Verlag GmbH & Co. KGaA)
      As a result of the booming biodiesel and oleochems. manufg. taking place worldwide since more than a decade, 2 million tonnes of glycerol consistently reach the market every year, even though after a decade of growth the total glycerol supply is expected to slightly decrease in 2014. Today the supply of glycerol is entirely independent of its demand, as there is as much glycerol as the amt. of vegetable oils and animal fats are hydrolyzed to make oleochems., or transesterified to produce biodiesel. This unique situation has led to consistently low glycerol prices, which initiated both the market penetration of glycerol in countries where it was not used due to traditional high price, as well as new uses of glycerol as raw material for the prodn. of value added chems. This article sheds light on the market of this uniquely versatile chem. whose no. of applications is unique amid all existing chems. About 2 million tonnes of glycerol consistently reach the market every year, even though after a decade of growth the total glycerol supply is expected to slightly decrease in 2014. Today the supply of glycerol is entirely independent of its demand, as there is as much glycerol as the amt. of vegetable oils and animal fats are hydrolyzed to make oleochems., or transesterified to produce biodiesel. This article sheds light on the market of this uniquely versatile chem. whose no. of applications is unique amid all existing chems.
    5. 5
      Coutanceau, C.; Baranton, S.; Kouamé, R. S. B. Selective Electrooxidation of Glycerol Into Value-Added Chemicals: A Short Overview. Front. Chem. 2019, 7, 100,  DOI: 10.3389/fchem.2019.00100
      5
      Selective electrooxidation of glycerol into value-added chemicals: a short overview
      Coutanceau, Christophe; Baranton, Steve; Kouame, Romeo S. Bitty
      Frontiers in Chemistry (Lausanne, Switzerland) (2019), 7 (), 100CODEN: FCLSAA; ISSN:2296-2646. (Frontiers Media S.A.)
      A review. A comprehensive overview of the catalysts developed for the electrooxidn. of glycerol with the aim of producing selectively value-added compds. is proposed in the present contribution. By presenting the main results reported in the literature on glycerol electrooxidn. in acidic and alk. media, using different kinds of catalytic materials (monometallic catalysts based on platinum group metals and non-noble metals, multimetallic alloys, or modification of surfaces by adatoms, etc.) and under different exptl. conditions, some general trends concerning the effects of catalyst compn. and structure, of reaction medium and of the electrode potential to enhance the activity for the glycerol oxidn. reaction and of the selectivity toward a unique value-added product will be presented and discussed. The objective is to provide a guideline for the development of electrochem. systems which allow performing the electrooxidn. of glycerol at the rate and selectivity as high as possible.
    6. 6
      Simões, M.; Baranton, S.; Coutanceau, C. Electrochemical Valorisation of Glycerol. ChemSusChem 2012, 5 (11), 2106– 2124,  DOI: 10.1002/cssc.201200335
      6
      Electrochemical valorisation of glycerol
      Simoes, Mario; Baranton, Steve; Coutanceau, Christophe
      ChemSusChem (2012), 5 (11), 2106-2124CODEN: CHEMIZ; ISSN:1864-5631. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A review. The worldwide glycerol stocks are increasing; to make the biodiesel industry sustainable economically, this chem. could be used as a secondary primary raw material. Elec. energy or hydrogen and added-value-chem. cogeneration becomes more and more an important research topic for increasing economical and industrial interests towards electrochem. technologies. Studies on glycerol electrooxidn. for fuel or electrolysis cell applications are scarce. The valorisation of glycerol is generally performed by org. chem. reactions forming, for example, esters, glycerol carbonates, ethers, acetals or ketals. Glycerol oxidn. is made up of complex pathway reactions that can produce a large no. of useful intermediates or valuable fine chems. with presently limited market impact due to expensive prodn. processes. Many of these chem. oxidn. routes lead to significant amts. of undesired byproducts, and enzymic processes are limited. Converse to classical heterogeneous processes, electrocatalytic oxidn. processes can be tuned by controlling the nature, compn. and structure of the electrocatalyst as well as the electrode potential. Such control may lead to very high selectivity and activity, avoiding or limiting product sepn. steps. The coupling of glycerol oxidn. to produce chems. with the oxygen redn. reaction in a fuel cell or water redn. reaction in an electrolysis cell on Pt-free catalysts results either in coprodn. of elec. energy or hydrogen for energy storage.
    7. 7
      Houache, M. S. E.; Hughes, K.; Baranova, E. A. Study on Catalyst Selection for Electrochemical Valorization of Glycerol. Sustainable Energy Fuels 2019, 3 (8), 1892– 1915,  DOI: 10.1039/C9SE00108E
      7
      Study on catalyst selection for electrochemical valorization of glycerol
      Houache, Mohamed S. E.; Hughes, Kara; Baranova, Elena A.
      Sustainable Energy & Fuels (2019), 3 (8), 1892-1915CODEN: SEFUA7; ISSN:2398-4902. (Royal Society of Chemistry)
      A review. The recent tremendous growth of biodiesel prodn. from vegetable oils or waste fats has led to increased glycerol accumulation as a byproduct of this process. This sparked attention towards glycerol use and valorization of this largely available and cheap compd. A no. of high value-added chems. could be produced from glycerol via different catalytic processes, ranging from heavy metal complexing agents to drug delivery agents or polymer precursors. Among several routes for glycerol valorization, the electrochem. one appears to be a very attractive process that can generate a no. of high purity value-added chems. Furthermore, the glycerol electrooxidn. reaction (GEOR) at the anode can be coupled with cathodic hydrogen prodn. or CO2 electroredn. in an electrolytic cell. The control of catalytic activity and selectivity is influenced by the nature, structure and compn. of the electrode material, which can be tuned by various synthesis approaches. This review provides a comprehensive summary and crit. anal. on glycerol electrochem. oxidn. research during the last five years. The main emphasize is made on catalyst selection, design and characterization for application in the GEOR. In particular, the recent development and prospects of using non-platinum group metal catalysts for glycerol electrooxidn. are discussed. Reaction product selectivity anal. using spectroscopic and anal. techniques is outlined. In addn., recent theor. developments, based on d. functional theory (DFT) calcns., are addressed as a tool for guiding the catalyst design with bespoke reaction selectivity and catalytic activity properties. Finally, the remaining challenges and prospects are also highlighted.
    8. 8
      Holade, Y.; Tuleushova, N.; Tingry, S.; Servat, K.; Napporn, T. W.; Guesmi, H.; Cornu, D.; Kokoh, K. B. Recent Advances in the Electrooxidation of Biomass-Based Organic Molecules for Energy, Chemicals and Hydrogen Production. Catal. Sci. Technol. 2020, 10 (10), 3071– 3112,  DOI: 10.1039/C9CY02446H
      8
      Recent advances in the electrooxidation of biomass-based organic molecules for energy, chemicals and hydrogen production
      Holade, Yaovi; Tuleushova, Nazym; Tingry, Sophie; Servat, Karine; Napporn, Teko W.; Guesmi, Hazar; Cornu, David; Kokoh, K. Boniface
      Catalysis Science & Technology (2020), 10 (10), 3071-3112CODEN: CSTAGD; ISSN:2044-4753. (Royal Society of Chemistry)
      A review. Electrosynthesis, a historically powerful tool for the prodn. of a no. of industrial-scale inorg. or org. materials, has experienced a renaissance over the last 10 years with research efforts seeking a dual prodn. platform for mols. and energy carriers. It is termed a Power-to-X approach. Specifically, H (H2) is a key compd. in emerging energy conversion and storage systems, acting as an energy carrier to provide elec. energy with a significantly reduced environmental footprint through H2/O2 fuel cells. The clean energy prodn. strategy from energy carriers is inversely termed an X-to-Power approach. However, H2 sources remain up to now the main key challenge. Increasing interest surrounds the development of advanced low energy consumption electrolysis cells enabling reliable, sustainable and dual prodn. of both H2 and valuable chems. from the selective oxidn. of surplus biomass-derivs. It can thus be summed up that the tremendous idea of generating electricity or producing fuels such as H2 while synthesizing chems. is an attractive pathway for org. synthesis and electricity prodn. However, precisely how this could be achieved in a cheap and sustainable way remains a puzzle for scientists. However, orgs. selective electrooxidn. reactions are central topics and bridge fuel cell and electrolysis cell research. A no. of (bio)catalytic interfaces have been developed to overcome their sluggish electrochem. kinetics. Within this perspective, the authors propose a detailed review on the recent advances over the last 10 years in co-generative fuel cells and electrolysis cells that operate with biomass-based org. mols. (EtOH, ethylene glycol, glycerol, (oligo)saccharides, cellulose, hemicellulose) while highlighting exptl. and theor. research that unifies those fields to yield devices with improved performance. The identified main electrocatalytic reaction descriptors allow for new materials to be proposed, which could enable maximized activity, selectivity and durability of anode materials. This perspective particularly enlightens the missing fundamental knowledge on parameters dictating electrocatalysis of org. compds. in aq. media. Overall, the implications for the wider scientific community of electrochem., electrocatalysis, materials science and org. chem., and finally provide several logical pathways and guidelines to stimulate progress, inspiring the development of org.-fuelled cogeneration electrochem. devices are discussed.
    9. 9
      Wu, J.; Yang, X.; Gong, M. Recent Advances in Glycerol Valorization via Electrooxidation: Catalyst, Mechanism and Device. Chin. J. Catal. 2022, 43 (12), 2966– 2986,  DOI: 10.1016/S1872-2067(22)64121-4
      9
      Recent advances in glycerol valorization via electrooxidation: Catalyst, mechanism and device
      Wu, Jianxiang; Yang, Xuejing; Gong, Ming
      Chinese Journal of Catalysis (2022), 43 (12), 2966-2986CODEN: CJCHCI; ISSN:1872-2067. (Elsevier B.V.)
      A review. Glycerol is one of the most important biomass-based platform mols., massively produced as a byproduct in the biodiesel industry. Its high purifn. cost from the crude glycerol raw material limits its application and demands new strategies for valorization. Compared to the conventional thermocatalytic strategies, the electrocatalytic strategies can not only enable the selective conversion at mild conditions but also pair up the cathodic reactions for the co-prodn. with higher efficiencies. In this review, we summarize the recent advances of catalyst designs and mechanistic understandings for the electrocatalytic glycerol oxidn. (GOR), and aim to provide an overview of the GOR process and the intrinsic structural-activity correlation for inspiring future work in this field. The review is dissected into three sections. We will first introduce the recent efforts of designing more efficient and selective catalysts for GOR, especial toward the prodn. of value-added products. Then, we will summarize the current understandings about the reaction network based on the ex-situ and in-situ spectroscopic studies as well as the theor. works. Lastly, we will select some representative examples of creating real electrochem. devices for the valorization of glycerol. By summarizing these previous efforts, we will provide our vision of future directions in the field of GOR toward real applications.
    10. 10
      Ge, R.; Li, J.; Duan, H. Recent Advances in Non-Noble Electrocatalysts for Oxidative Valorization of Biomass Derivatives. Sci. China Mater. 2022, 65 (12), 3273– 3301,  DOI: 10.1007/s40843-022-2076-y
      10
      Recent advances in non-noble electrocatalysts for oxidative valorization of biomass derivatives
      Ge, Ruixiang; Li, Jing; Duan, Haohong
      Science China Materials (2022), 65 (12), 3273-3301CODEN: SCMCDB; ISSN:2095-8226. (Science China Press)
      A review. Electrocatalysis is deemed as a promising approach for sustainable energy conversion and chem. prodn. Although a variety of cathode reactions (e.g., hydrogen evolution and CO2/N2 redn.) produce valuable fuels and chems., the extensively studied oxygen evolution reaction (OER) at anode only generates O2, which is not a high-value product. Substituting the OER with thermodynamically more favorable biomass deriv. oxidn. reactions (BDORs) not only enables energy-saving electrocatalysis, but also provides value-added anode products. Recent achievements have demonstrated that non-noble electrocatalysts are promising for BDORs. Herein, we provide a comprehensive review on recent achievements in the field of electrochem. BDORs catalyzed by non-noble catalysts. We start by summarizing the electrocatalytic oxidn. of different types of biomass-derived substrates, aiming to show the advantages of the electrocatalytic pathway and to introduce the state-of-the-art non-noble catalysts. The reaction mechanisms of non-noble-material-catalyzed BDORs are then summarized and classified into three types according to the acceptor of hydrogen species during the dehydrogenation of biomass derivs. Subsequently, discussions are devoted to the strategies for promoting the performances of non-noble electrocatalysts. Finally, we propose our opinions regarding future trends and major challenges in this field.
    11. 11
      Simões, M.; Baranton, S.; Coutanceau, C. Electro-Oxidation of Glycerol at Pd Based Nano-Catalysts for an Application in Alkaline Fuel Cells for Chemicals and Energy Cogeneration. Appl. Catal., B 2010, 93 (3–4), 354– 362,  DOI: 10.1016/j.apcatb.2009.10.008
      11
      Electro-oxidation of glycerol at Pd based nano-catalysts for an application in alkaline fuel cells for chemicals and energy cogeneration
      Simoes, Mario; Baranton, Steve; Coutanceau, Christophe
      Applied Catalysis, B: Environmental (2010), 93 (3-4), 354-362CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
      C-supported Pd, Pt, Au and bimetallic PdAu and PdNi nano-catalysts with different compns. were synthesized. Their catalytic activity toward glycerol electrooxidn. was evaluated in alk. medium. Phys. and electrochem. methods where used to characterize the structure and the surface of the catalysts. The PdxAu1-x/C catalysts were alloys, which present an increase of crystallite (XRD) and particle (TEM) sizes with increasing Au at. fraction. Their surfaces were Pd rich whatever the Pd at. ratio. The structure of the Pd0.5Ni0.5/C catalyst is much more difficult to understand, but it seems to be composed of a Pd phase in interaction with a Ni(OH)2 phase. The onset potential of glycerol oxidn. is ∼0.15 V lower on Pt/C than on Pd/C and Au/C. All PdxMe1-x/C catalysts presented a lower onset potential than monometallic Au/C and Pd/C ones, but higher than Pt/C. For bimetallic catalysts, the order of activity at low potentials is: Pd0.3Au0.7/C > Pd0.5Au0.5/C > Pd0.5Ni0.5/C. Electrochem. expts. and in situ IR spectroscopy showed that glycerol electrooxidn. mechanism is dependent on the catalyst, leading to different reaction products. Adsorbed CO species are detected on monometallic Pt and on Pd-rich catalysts, but not on Au and Pd0.3Au0.7 catalysts, indicating that they cannot break the C-C bond. The formation of hydroxypyruvate ion, which is a costly chem. product, is detected on pure Au catalyst.
    12. 12
      Chen, X.; Granda-Marulanda, L. P.; McCrum, I. T.; Koper, M. T. M. How Palladium Inhibits CO Poisoning during Electrocatalytic Formic Acid Oxidation and Carbon Dioxide Reduction. Nat. Commun. 2022, 13 (1), 38,  DOI: 10.1038/s41467-021-27793-5
      12
      How palladium inhibits CO poisoning during electrocatalytic formic acid oxidation and carbon dioxide reduction
      Chen, Xiaoting; Granda-Marulanda, Laura P.; McCrum, Ian T.; Koper, Marc T. M.
      Nature Communications (2022), 13 (1), 38CODEN: NCAOBW; ISSN:2041-1723. (Nature Portfolio)
      Development of reversible and stable catalysts for the electrochem. redn. of CO2 is of great interest. Here, we elucidate the atomistic details of how a palladium electrocatalyst inhibits CO poisoning during both formic acid oxidn. to carbon dioxide and carbon dioxide redn. to formic acid. We compare results obtained with a platinum single-crystal electrode modified with and without a single monolayer of palladium. We combine (high-scan-rate) cyclic voltammetry with d. functional theory to explain the absence of CO poisoning on the palladium-modified electrode. We show how the high formate coverage on the palladium-modified electrode protects the surface from poisoning during formic acid oxidn., and how the adsorption of CO precursor dictates the delayed poisoning during CO2 redn. The nature of the hydrogen adsorbed on the palladium-modified electrode is considerably different from platinum, supporting a model to explain the reversibility of this reaction. Our results help in designing catalysts for which CO poisoning needs to be avoided.
    13. 13
      Oliveira, V. L.; Morais, C.; Servat, K.; Napporn, T. W.; Tremiliosi-Filho, G.; Kokoh, K. B. Glycerol Oxidation on Nickel Based Nanocatalysts in Alkaline Medium - Identification of the Reaction Products. J. Electroanal. Chem. 2013, 703, 56– 62,  DOI: 10.1016/j.jelechem.2013.05.021
      13
      Glycerol oxidation on nickel based nanocatalysts in alkaline medium - Identification of the reaction products
      Oliveira, V. L.; Morais, C.; Servat, K.; Napporn, T. W.; Tremiliosi-Filho, G.; Kokoh, K. B.
      Journal of Electroanalytical Chemistry (2013), 703 (), 56-62CODEN: JECHES; ISSN:1873-2569. (Elsevier B.V.)
      Carbon-supported Ni-based nanoparticles were prepd. by the impregnation method and used as anode electrocatalysts for glycerol conversion. These metallic powders were mixed with a suitable amt. of a Nafion/water soln. to make catalytic inks which were then deposited onto the surface of C Toray used as a conductive substrate. Long-term electrolyzes of glycerol were carried out in alk. medium by chronoamperometry expts. Anal. of the oxidn. products was performed with ion-exclusion liq. chromatog. which separates the analytes by ascending pKa. The spectroscopic measurements showed that the Co content in the anode compn. did contribute to the CC bond cleavage of the initial mol. of glycerol.
    14. 14
      Holade, Y.; Morais, C.; Arrii-Clacens, S.; Servat, K.; Napporn, T. W.; Kokoh, K. B. New Preparation of PdNi/C and PdAg/C Nanocatalysts for Glycerol Electrooxidation in Alkaline Medium. Electrocatalysis 2013, 4 (3), 167– 178,  DOI: 10.1007/s12678-013-0138-1
      14
      New Preparation of PdNi/C and PdAg/C Nanocatalysts for Glycerol Electrooxidation in Alkaline Medium
      Holade, Yaovi; Morais, Claudia; Arrii-Clacens, S.; Servat, K.; Napporn, T. W.; Kokoh, K. B.
      Electrocatalysis (2013), 4 (3), 167-178CODEN: ELECCF; ISSN:1868-2529. (Springer)
      PdAg/C and PdNi/C nanomaterials with different at. compns. were successfully synthesized by a "bromide anion exchange" method and applied to the glycerol electrooxidn. in alk. medium. The catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), differential and thermogravimetric anal., electrochem. cyclic voltammetry, CO stripping, and spectroelectrochem. XRD showed a small crystallite size between 3 and 4 nm for PdNi/C, and 3 and 6 nm for PdAg/C. TEM results showed a good dispersion of the particles on the carbon support and a particle mean size ranging from 3.73 to 3.97 nm. The electrochem. expts. have highlighted a high specific electrochem. surface area for the different catalysts such as 69.20 m2 g-1 for Pd/C. Furthermore, all the bimetallic catalysts exhibited a good kinetic towards glycerol electrooxidn. when compared to the monometallic material Pd/C and at lower potential values. The Pd60Ni40/C catalyst is outstandingly active, being therefore a good candidate for electrochem. valorization of glycerol conversion.
    15. 15
      Holade, Y.; Morais, C.; Servat, K.; Napporn, T. W.; Kokoh, K. B. Toward the Electrochemical Valorization of Glycerol: Fourier Transform Infrared Spectroscopic and Chromatographic Studies. ACS Catal. 2013, 3 (10), 2403– 2411,  DOI: 10.1021/cs400559d
      15
      Toward the Electrochemical Valorization of Glycerol: Fourier Transform Infrared Spectroscopic and Chromatographic Studies
      Holade, Yaovi; Morais, Claudia; Servat, Karine; Napporn, Teko W.; Kokoh, K. Boniface
      ACS Catalysis (2013), 3 (10), 2403-2411CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
      Glycerol electrooxidn. reaction was studied by electrochem., spectroelectrochem., and chromatog. methods on Pd-Ni and Pd-Ag nanoparticules supported on C Vulcan XC 72R. These materials, prepd. by the so-called Bromide Anion Exchange method, exhibited high activity toward the glycerol electrooxidn. in alk. medium showing also an important shift of the onset potential toward low potential values. Electrolysis coupled with HPLC and in situ FTIR spectroscopy (FTIRS) measurements were used to det. the various compds. generated in the oxidative conversion of this three hydroxyl groups C mol. Some products with high added value such as glycerate and tartronate were identified. In situ FTIRS results also showed the pH decrease in the thin layer near the electrode. These results will pos. serve as guidelines for future works on the potential use of glycerol in fuel cell devices in a cogeneration of high value chems. and energy process.
    16. 16
      White, J.; Anil, A.; Martín-Yerga, D.; Salazar-Alvarez, G.; Henriksson, G.; Cornell, A. Electrodeposited PdNi on a Ni Rotating Disk Electrode Highly Active for Glycerol Electrooxidation in Alkaline Conditions. Electrochim. Acta 2022, 403, 139714,  DOI: 10.1016/j.electacta.2021.139714
      16
      Electrodeposited PdNi on a Ni rotating disk electrode highly active for glycerol electrooxidation in alkaline conditions
      White, Jai; Anil, Athira; Martin-Yerga, Daniel; Salazar-Alvarez, German; Henriksson, Gunnar; Cornell, Ann
      Electrochimica Acta (2022), 403 (), 139714CODEN: ELCAAV; ISSN:0013-4686. (Elsevier Ltd.)
      The development of alc.-based electrolysis to enable the concurrent prodn. of hydrogen with low electricity consumption still faces major challenges in terms of the max. anodic c.d. achievable. While noble metals enable a low electrode potential to facilitate alc. oxidn., the deactivation of the catalyst at higher potentials makes it difficult for the obtained anodic c.d. to compete with water electrolysis. In this work the effect of significant parameters such as mass transport, glycerol and OH- concn. and electrolyte temp. on the glycerol electrooxidn. reaction (GEOR) in alk. conditions on a bimetallic catalyst PdNi/NiRDE (Pd0.9Ni0.1) has been studied to discern exptl. conditions which maximise achievable anodic c.d. before deactivation occurs. The ratio of NaOH:glycerol in the electrolyte highly affects the rate of the GEOR. A max. c.d. of 793 mA cm-2 at -0.125 V vs. Hg/HgO through steady state polarisation curves was achieved at a moderate and intermediate rotation rate of 500 RPM in a 2 M NaOH and 1 M glycerol (ratio of 2) electrolyte at 80°C. Shown here is a method of catalyst reactivation for enabling the long-term use of the PdNi/NiRDE for electrolysis at optimal conditions for extended periods of time (3 h at 300 mA cm-2 and 10 h at 100 mA cm-2). Through SEM (SEM), X-ray photon electron spectroscopy (XPS) and X-ray diffraction (XRD) it is shown that the electrodeposition of Pd and Ni forms an alloy and that after 10 h of electrolysis the catalyst has chem. and structural stability. This study provides details on parameters significant to the maximising of the GEOR c.d. and the minimising of the debilitating effect that deactivation has on noble metal based electrocatalysts for the GEOR.
    17. 17
      Koper, M. T. M. Structure Sensitivity and Nanoscale Effects in Electrocatalysis. Nanoscale 2011, 3 (5), 2054– 2073,  DOI: 10.1039/c0nr00857e
      17
      Structure sensitivity and nanoscale effects in electrocatalysis
      Koper, Marc T. M.
      Nanoscale (2011), 3 (5), 2054-2073CODEN: NANOHL; ISSN:2040-3372. (Royal Society of Chemistry)
      A review discusses the role of the detailed nanoscale structure of catalytic surfaces on the activity of various electrocatalytic reactions of importance for fuel cells, H prodn., and other environmentally important catalytic reactions, such as CO oxidn., MeOH and EtOH oxidn., NH3 oxidn., nitric oxide redn., H evolution, and O redn. Specifically, results and insights obtained from surface-science single-crystal-based model expts. are linked to expts. on well-defined shape-controlled nanoparticles. A classification of structure sensitive effects in electrocatalysis is suggested, based both on empirical grounds and on quantum-chem. viz. thermochem. considerations. The mutual relation between the two classification schemes is also discussed. The review underscores the relevance of single-crystal modeling of nanoscale effects in catalysis, and points to the special role of two kinds of active sites for electrocatalysis on nanoparticulate surfaces: (i) steps and defects in (111) terraces or facets, and (ii) long-range (100) terraces or facets.
    18. 18
      Li, R.; Wei, Z.; Huang, T.; Yu, A. Ultrasonic-Assisted Synthesis of Pd-Ni Alloy Catalysts Supported on Multi-Walled Carbon Nanotubes for Formic Acid Electrooxidation. Electrochim. Acta 2011, 56 (19), 6860– 6865,  DOI: 10.1016/j.electacta.2011.05.097
      18
      Ultrasonic-assisted synthesis of Pd-Ni alloy catalysts supported on multi-walled carbon nanotubes for formic acid electrooxidation
      Li, Ruoshi; Wei, Zhen; Huang, Tao; Yu, Aishui
      Electrochimica Acta (2011), 56 (19), 6860-6865CODEN: ELCAAV; ISSN:0013-4686. (Elsevier Ltd.)
      Pd-Ni alloys with different compns. (i.e. Pd2Ni, PdNi, PdNi2) dispersed on multi-walled C nanotubes (MWCNTs) were prepd. by ultrasonic-assisted chem. redn. The XRD patterns indicate that all Pd and Pd-Ni nanoparticles exist as Pd fcc. structure, while Ni alloys with Pd. The TEM images show the addn. of Ni decreases the particle size and improves the dispersion. The XPS spectra demonstrate the electronic modification of Pd by Ni doping. The electrochem. measurements reveal that the PdNi catalysts have better catalytic activity and stability for formic acid electrooxidn., among them PdNi/MWCNTs is the best. The performance enhancement is ascribed to the increase of electroactive surface area (EASA) and Ni doping effect which might modify the electronic structure.
    19. 19
      Du, C.; Chen, M.; Wang, W.; Yin, G. Nanoporous PdNi Alloy Nanowires As Highly Active Catalysts for the Electro-Oxidation of Formic Acid. ACS Appl. Mater. Interfaces 2011, 3 (2), 105– 109,  DOI: 10.1021/am100803d
      19
      Nanoporous PdNi Alloy Nanowires As Highly Active Catalysts for the Electro-Oxidation of Formic Acid
      Du, Chunyu; Chen, Meng; Wang, Wengang; Yin, Geping
      ACS Applied Materials & Interfaces (2011), 3 (2), 105-109CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
      Highly active and durable catalysts for formic acid oxidn. are crucial to the development of direct formic acid fuel cell. In this letter, we report the synthesis, characterization, and electrochem. testing of nanoporous Pd57Ni43 alloy nanowires for use as the electrocatalyst towards formic acid oxidn. These nanowires are prepd. by chem. dealloying of Ni from Ni-rich PdNi alloy nanowires, and have high surface area. X-ray diffraction data show that the Pd57Ni43 nanowires have the face-centered cubic cryst. structure of pure Pd, whereas XPS confirms the modification of electronic structure of Pd by electron transfer from Ni to Pd. Electrocatalytic activity of the nanowires towards formic acid oxidn. exceeds that of the state-of-the-art Pd/C. More importantly, the nanowires are highly resistant to deactivation. It is proposed that the high active surface area and modulated surface properties by Ni are responsible for the improvement of activity and durability. Dealloyed nanoporous Pd57Ni43 alloy nanowires are thus proposed as a promising catalyst towards formic acid oxidn.
    20. 20
      López-Coronel, A.; Torres-Pacheco, L. J.; Bañuelos, J. A.; Álvarez-López, A.; Guerra-Balcázar, M.; Álvarez-Contreras, L.; Arjona, N. Highly Active PdNi Bimetallic Nanocubes Electrocatalysts for the Ethylene Glycol Electro-Oxidation in Alkaline Medium. Appl. Surf. Sci. 2020, 530, 147210,  DOI: 10.1016/j.apsusc.2020.147210
      20
      Highly active PdNi bimetallic nanocubes electrocatalysts for the ethylene glycol electro-oxidation in alkaline medium
      Lopez-Coronel, Andres; Torres-Pacheco, Luis J.; Banuelos, Jennifer A.; Alvarez-Lopez, Alejandra; Guerra-Balcazar, Minerva; Alvarez-Contreras, Lorena; Arjona, Noe
      Applied Surface Science (2020), 530 (), 147210CODEN: ASUSEE; ISSN:0169-4332. (Elsevier B.V.)
      Sub <10 nm PdNi bimetallic nanocubes were used as electrocatalysts for the ethylene glycol electrooxidn. reaction (EGOR) in alk. media. Pd nanocubes were obtained and used as ref. material. Spectroscopic tests indicated that materials labeled as Pd80Ni20/C, Pd70Ni30/C and Pd60Ni40/C were obtained. High-resoln. transmission electron micrographs (HR-TEM) revealed nanocubes-like shapes in all materials, being particularly abundant in Pd80Ni20/C and Pd60Ni40/C. Pd70Ni30/C presented a mixt. of hemispheres and nanocubes. Av. particle sizes of ∼6 nm were detd. for Pd80Ni20/C and Pd60Ni40/C, while Pd70Ni30/C had particle sizes of 5.6 nm. XPS concluded that Ni was as Ni-(oxy) hydroxides (NiOOH), providing oxygenated species in the EGOR and thus, improving the electron transfer, as was corroborated by electrochem. impedance spectroscopy (EIS). In this manner, Pd70Ni30/C and Pd60Ni40/C displayed superior activity at 1 M EG + 2 M KOH than Pd nanocubes and Pd80Ni20/C, achieving current densities close to 320 mA cm-2. The increase of temp. to 50° resulted beneficial for Pd70Ni30/C, displaying a max. c.d. of 501.08 mA cm-2.
    21. 21
      Guo, M.; Wang, H.; Cui, L.; Zhang, J.; Xiang, Y.; Lu, S. Nickel Promoted Palladium Nanoparticles for Electrocatalysis of Carbohydrazide Oxidation Reaction. Small 2019, 15 (28), 1900929,  DOI: 10.1002/smll.201900929
      There is no corresponding record for this reference.
    22. 22
      Shen, S. Y.; Zhao, T. S.; Xu, J. B.; Li, Y. S. Synthesis of PdNi Catalysts for the Oxidation of Ethanol in Alkaline Direct Ethanol Fuel Cells. J. Power Sources 2010, 195 (4), 1001– 1006,  DOI: 10.1016/j.jpowsour.2009.08.079
      22
      Synthesis of PdNi catalysts for the oxidation of ethanol in alkaline direct ethanol fuel cells
      Shen, S. Y.; Zhao, T. S.; Xu, J. B.; Li, Y. S.
      Journal of Power Sources (2010), 195 (4), 1001-1006CODEN: JPSODZ; ISSN:0378-7753. (Elsevier B.V.)
      Carbon-supported PdNi catalysts for the ethanol oxidn. reaction in alk. direct ethanol fuel cells are successfully synthesized by the simultaneous redn. method using NaBH4 as reductant. X-ray diffraction characterization confirms the formation of the face-centered cubic cryst. Pd and Ni(OH)2 on the carbon powder for the PdNi/C catalysts. Transmission electron microscopy images show that the metal particles are well-dispersed on the carbon powder, while energy-dispersive X-ray spectrometer results indicate the uniform distribution of Ni around Pd. XPS analyses reveal the chem. states of Ni, including metallic Ni, NiO, Ni(OH)2 and NiOOH. Cyclic voltammetry and chronopotentiometry tests demonstrate that the Pd2Ni3/C catalyst exhibits higher activity and stability for the ethanol oxidn. reaction in an alk. medium than does the Pd/C catalyst. Fuel cell performance tests show that the application of Pd2Ni3/C as the anode catalyst of an alk. direct ethanol fuel cell with an anion-exchange membrane can yield a max. power d. of 90 mW cm-2 at 60 °C.
    23. 23
      Miao, B.; Wu, Z.-P.; Zhang, M.; Chen, Y.; Wang, L. Role of Ni in Bimetallic PdNi Catalysts for Ethanol Oxidation Reaction. J. Phys. Chem. C 2018, 122 (39), 22448– 22459,  DOI: 10.1021/acs.jpcc.8b05812
      23
      Role of Ni in Bimetallic PdNi Catalysts for Ethanol Oxidation Reaction
      Miao, Bei; Wu, Zhi-Peng; Zhang, Minhua; Chen, Yifei; Wang, Lichang
      Journal of Physical Chemistry C (2018), 122 (39), 22448-22459CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      Bimetallic PdNi catalysts have garnered great interest in the study of ethanol oxidn. reactions (EORs), though mechanistic insights into their catalytic performances are lacking, which hinders further improvement and rational design of the next generation of PdNi catalysts. As such, d. functional theory (DFT) calcns. were performed for six key elementary reactions using four model catalysts, one with pure Pd and three for PdNi. DFT results indicate that the reduced catalytic activities obsd. exptl. when Ni atoms were placed under Pd layers are the result of an increase in the reaction barrier for CH3COOH formation. Further anal. illustrated that this is largely owing to the charge transfer from the Ni to the Pd atoms. On the other hand, the enhanced activities of the PdNi catalysts with respect to pure Pd catalysts in EORs when Ni atoms are exposed at the catalyst surfaces are due to the lowering of the reaction barrier toward C-C bond cleavage and increasing of that toward C-O bond coupling. Therefore, surface Ni atoms are responsible for the superior activity of the PdNi catalysts in EORs. Further anal. of DFT results suggests that the reaction barriers of the C-C bond cleavage and the C-O bond coupling approach similar values when the compn. of surface Ni atoms in a PdNi catalyst reaches about 44%. To achieve a complete EOR, the estd. surface Ni atoms should be as high as 77%. However, stability may become a concern for catalysts with such a high exposure of Ni atoms at the catalyst surface.
    24. 24
      Yang, H.; Wang, H.; Li, H.; Ji, S.; Davids, M. W.; Wang, R. Effect of Stabilizers on the Synthesis of Palladium-Nickel Nanoparticles Supported on Carbon for Ethanol Oxidation in Alkaline Medium. J. Power Sources 2014, 260, 12– 18,  DOI: 10.1016/j.jpowsour.2014.02.110
      24
      Effect of stabilizers on the synthesis of palladium-nickel nanoparticles supported on carbon for ethanol oxidation in alkaline medium
      Yang, Huijuan; Wang, Hui; Li, Hao; Ji, Shan; Davids, Moegamat Wafeeq; Wang, Rongfang
      Journal of Power Sources (2014), 260 (), 12-18CODEN: JPSODZ; ISSN:0378-7753. (Elsevier B.V.)
      PdNi/C electrocatalysts for ethanol oxidn. in alk. medium are fabricated using four stabilizers, i.e., glycine (G), ethylene diamine tetraacetic acid (EDTA), sodium citrate (SC), and sodium dodecyl sulfate (SDS) with the same reducing process and reaction parameters. X-ray diffraction characterization shows PdNi nanoparticles for all PdNi/C electrocatalysts possess face-centered cubic structure with different alloying degree. TEM results show that PdNi/C-G and PdNi/C-SC have uniform dispersion with ellipse morphol., while particle agglomeration occurs on PdNi/C-EDTA and PdNi/C-SDS. Electrocatalytic activities of these PdNi/C electrocatalysts for ethanol oxidn. are measured by cyclic voltammetry and chronoamperometry techniques. The electrocatalytic activities of PdNi/C change with the different lattice contraction. PdNi/C-SC electrocatalyst exhibits the best activity among the four electrocatalysts, which is ascribed to an appropriate lattice contraction.
    25. 25
      Dutta, A.; Datta, J. Energy Efficient Role of Ni/NiO in PdNi Nano Catalyst Used in Alkaline DEFC. J. Mater. Chem. A 2014, 2 (9), 3237– 3250,  DOI: 10.1039/c3ta12708g
      25
      Energy efficient role of Ni/NiO in PdNi nano catalyst used in alkaline DEFC
      Dutta, Abhijit; Datta, Jayati
      Journal of Materials Chemistry A: Materials for Energy and Sustainability (2014), 2 (9), 3237-3250CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
      The present study is based on a study of electrooxidn. of EtOH in alk. medium over the C supported PdxNiy catalyst formulations synthesized by simultaneous redn. of the precursors using Na borohydride as the reducing agent. X-ray diffraction studies of the PdNi/C nano-particles reveal formation of the fcc. cryst. Pd, NiO and Ni(OH)2 on a meso porous C support whereas XPS confirmed the presence of metallic Ni and the oxide phases NiO, Ni(OH)2, NiOOH in the catalyst matrix. The structure and morphol. of the binary matrix and the role of Ni and its oxide as a catalytically contributing entity in the oxidn. process was ascertained by the help of resp. anal. techniques like TEM, XRD, XPS, voltammetry and chronoamperometry. Sequential oxidn. steps were suggested involving dimeric (NiO)2 as one of the intermediate species during the oxidn. reaction proceeding towards aldehyde formation and further to carbonate prodn. via the intermediate formation of a 6 member ring, thereby increasing the reaction rates. This phenomenon was discussed at mol. level using the results obtained from XPS anal. The observations were further accomplished by extending the work to ion chromatog. for quant. anal. of the products formed during oxidn. of EtOH. All the above results are congruent with the mechanistic interpretation and reflect the paramount significance of NiO existing in the binary catalyst matrix for accelerating EtOH oxidn. reaction kinetics at a temp. 40° and above.
    26. 26
      Zhao, Y.; Yang, X.; Tian, J.; Wang, F.; Zhan, L. Methanol Electro-Oxidation on Ni@Pd Core-Shell Nanoparticles Supported on Multi-Walled Carbon Nanotubes in Alkaline Media. Int. J. Hydrogen Energy 2010, 35 (8), 3249– 3257,  DOI: 10.1016/j.ijhydene.2010.01.112
      26
      Methanol electro-oxidation on Ni@Pd core-shell nanoparticles supported on multi-walled carbon nanotubes in alkaline media
      Zhao, Yanchun; Yang, Xiulin; Tian, Jianniao; Wang, Fengyang; Zhan, Lu
      International Journal of Hydrogen Energy (2010), 35 (8), 3249-3257CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
      A novel method to prep. well-dispersed Ni@Pd core-shell nanoparticles on multi-walled carbon nanotubes (Ni@Pd/MWCNTs) is reported. The morphol. and crystallinity of the catalyst are characterized by SEM, transmission electron microscopy (TEM), XPS and X-ray diffraction (XRD) analyses, resp. Binary composite Ni@Pd/MWCNTs have been obtained and investigated for electrocatalysis of methanol oxidn. in 0.5 M NaOH. It is obsd. that Ni@Pd/MWCNTs increases the apparent electrocatalytic activity and stability of the electrode considerably than that of PdNi/MWCNTs and Pd/MWCNTs catalysts. It is implied that Ni@Pd core-shell nanoparticles supported on MWCNTs is very promising for portable applications in DMFC in alk. soln.
    27. 27
      Araujo, R. B.; Martín-Yerga, D.; Santos, E. C.; Cornell, A.; Pettersson, L. G. M. Elucidating the Role of Ni to Enhance the Methanol Oxidation Reaction on Pd Electrocatalysts. Electrochim. Acta 2020, 360, 136954,  DOI: 10.1016/j.electacta.2020.136954
      27
      Elucidating the role of Ni to enhance the methanol oxidation reaction on Pd electrocatalysts
      Araujo, Rafael B.; Martin-Yerga, Daniel; Santos, Egon Campos dos; Cornell, Ann; Pettersson, Lars G. M.
      Electrochimica Acta (2020), 360 (), 136954CODEN: ELCAAV; ISSN:0013-4686. (Elsevier Ltd.)
      Amongst promising available technologies enabling the transition to renewable energy sources, electrochem. oxidn. of alcs., in a direct fuel cell or in an electrolysis reaction (H2 prodn.), can be an economically and sustainable alternative to currently used technologies. The authors highlight the advantages of a Pd-Ni bimetallic electrocatalyst for MeOH electrooxidn. - a convenient choice due to the low cost of Ni combined with the obsd. acceptable catalytic performance of Pd. The authors report a synergistic effort between expts. and theor. calcns. based on d. functional theory to provide an in-depth understanding - at the atomistic level - of the origin of the enhanced electrochem. activity of MeOH electrooxidn. using the bimetallic catalysts Pd3Ni and PdNi over pure Pd. Cyclic voltammograms and High-Performance Liq. Chromatog. (HPLC) demonstrate higher activity towards MeOH electrooxidn. with increased Ni concn. and, also, higher selectivity for CO2. These effects are understood by: (1) changes in the MeOH oxidn. reaction mechanism. (2) Mitigation or suppression of CO poisoning on the Pd-Ni alloys as compared to the pure Pd catalyst. (3) A stronger tendency towards highly oxidized intermediates for the alloys. These findings elucidate the effects of a bimetallic electrocatalyst for alc. electrooxidn. as well as unambiguously suggest PdNi as a more cost-effective alternative electrocatalyst.
    28. 28
      Liu, Z.; Zhang, X.; Hong, L. Physical and Electrochemical Characterizations of Nanostructured Pd/C and PdNi/C Catalysts for Methanol Oxidation. Electrochem. Commun. 2009, 11 (4), 925– 928,  DOI: 10.1016/j.elecom.2009.02.030
      28
      Physical and electrochemical characterizations of nanostructured Pd/C and PdNi/C catalysts for methanol oxidation
      Liu, Zhaolin; Zhang, Xinhui; Hong, Liang
      Electrochemistry Communications (2009), 11 (4), 925-928CODEN: ECCMF9; ISSN:1388-2481. (Elsevier B.V.)
      Pd and PdNi nanoparticles supported on Vulcan XC-72 carbon were prepd. by a chem. redn. with formic acid process. The catalysts were characterized by TEM, XRD, cyclic voltammetry, and chronoamperometry. The Pd and PdNi nanoparticles, which were uniformly dispersed on carbon, were 2-10 nm in diams. The PdNi/C catalyst has higher electrocatalytic activity for methanol oxidn. in alk. media than a comparative Pd/C catalyst and shows great potential as less expensive electrocatalyst for methanol electrooxidn. in alk. media in direct methanol fuel cells.
    29. 29
      Martín-Yerga, D.; Yu, X.; Terekhina, I.; Henriksson, G.; Cornell, A. In Situ Catalyst Reactivation for Enhancing Alcohol Electro-Oxidation and Coupled Hydrogen Generation. Chem. Commun. 2020, 56 (28), 4011– 4014,  DOI: 10.1039/D0CC01321H
      29
      In situ catalyst reactivation for enhancing alcohol electro-oxidation and coupled hydrogen generation
      Martin-Yerga, Daniel; Yu, Xiaowen; Terekhina, Irina; Henriksson, Gunnar; Cornell, Ann
      Chemical Communications (Cambridge, United Kingdom) (2020), 56 (28), 4011-4014CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
      A novel method exploiting the in situ reactivation of a PdNi catalyst to enhance the electro-oxidn. of alcs. is reported. The periodic regeneration of the catalyst surface leads to significant gains in terms of conversion rate, energy requirements and stability compared to the conventional potentiostatic method.
    30. 30
      Martín-Yerga, D.; White, J.; Henriksson, G.; Cornell, A. Structure-Reactivity Effects of Biomass-Based Hydroxyacids for Sustainable Electrochemical Hydrogen Production. ChemSusChem 2021, 14 (8), 1902– 1912,  DOI: 10.1002/cssc.202100073
      30
      Structure-Reactivity Effects of Biomass-based Hydroxyacids for Sustainable Electrochemical Hydrogen Production
      Martin-Yerga, Daniel; White, Jai; Henriksson, Gunnar; Cornell, Ann
      ChemSusChem (2021), 14 (8), 1902-1912CODEN: CHEMIZ; ISSN:1864-5631. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Biomass electro-oxidn. is a promising approach for the sustainable generation of H2 by electrolysis with simultaneous synthesis of value-added chems. In this work, the electro-oxidn. of two structurally different org. hydroxyacids, lactic acid and gluconic acid, was studied comparatively to understand how the chem. structure of the hydroxyacid affects the electrochem. reactivity under various conditions. It was concluded that hydroxyacids such as gluconic acid, with a considerable d. of C-OH groups, are highly reactive and promising for the sustainable generation of H2 by electrolysis at low potentials and high conversion rates (less than -0.15 V vs. Hg/HgO at 400 mA cm-2) but with low selectivity to specific final products. In contrast, the lower reactivity of lactic acid did not enable H2 generation at very high conversion rates (<100 mA cm-2), but the reaction was significantly more selective (64 % to pyruvic acid). This work shows the potential of biomass-based org. hydroxyacids for sustainable generation of H2 and highlights the importance of the chem. structure on the reactivity and selectivity of the electro-oxidn. reactions.
    31. 31
      Ipadeola, A. K.; Lisa Mathebula, N. Z.; Pagliaro, M. V.; Miller, H. A.; Vizza, F.; Davies, V.; Jia, Q.; Marken, F.; Ozoemena, K. I. Unmasking the Latent Passivating Roles of Ni(OH)2 on the Performance of Pd-Ni Electrocatalysts for Alkaline Ethanol Fuel Cells. ACS Appl. Energy Mater. 2020, 3 (9), 8786– 8802,  DOI: 10.1021/acsaem.0c01314
      31
      Unmasking the Latent Passivating Roles of Ni(OH)2 on the Performance of Pd-Ni Electrocatalysts for Alkaline Ethanol Fuel Cells
      Ipadeola, Adewale Kabir; Lisa Mathebula, Nomxolisi Zakithi; Pagliaro, Maria Vincenza; Miller, Hamish Andrew; Vizza, Francesco; Davies, Veronica; Jia, Qingying; Marken, Frank; Ozoemena, Kenneth Ikechukwu
      ACS Applied Energy Materials (2020), 3 (9), 8786-8802CODEN: AAEMCQ; ISSN:2574-0962. (American Chemical Society)
      Nicked-based metal-org. framework-derived carbon (Ni/MOFDC) and its acid-treated counterpart (AT-Ni/MOFDC) have been prepd. as supports for palladium nanoparticle electrocatalysts (Pd/Ni/MOFDC and Pd/AT-Ni/MOFDC). These materials have been prepd. using facile microwave-assisted techniques. Several spectroscopic and microscopic techniques (such as FTIR, Raman, PXRD, XPS, XANES, FT-EXAFS, and TEM) have been used to thoroughly characterize physicochem. properties of the materials. It is revealed that acid treatment successfully cleaned the metallic Ni surface of the passivating hydroxides (Ni(OH)2 and NiOOH) to generate a very low concn. of Ni nanoparticles on the carbon support. The Ni-deficient Pd/AT-Ni/MOFDC shows excellent electrocatalytic performance toward ethanol oxidn. reaction (EOR) in the alk. medium compared to the Ni-hydroxide-rich Pd/Ni/MOFDC counterpart. As a proof-of-concept, these electrocatalysts have been employed as anodes and demonstrated for membraneless direct ethanol microfuel cells (μ-DEFCs) with a micro-3D-printed cell, with FeCo/C as electrocatalyst for the oxygen redn. reaction at the cathode. The Pd/AT-Ni/MOFDC displays increased peak power d. (Pm = 26.49 mW cm-2) with 68% voltage retention after a 24 h galvanostatic discharge test at 40 mA cm-2 and reduced impedance. The improved electrocatalytic properties of the Pd/AT-Ni/MOFDC underscore the need to clean the nickel surface of its passivating hydroxides to harness its full promotional activities toward alc. oxidn. reaction on precious metal electrocatalysts.
    32. 32
      del Rosario, J. A. D.; Ocon, J. D.; Jeon, H.; Yi, Y.; Lee, J. K.; Lee, J. Enhancing Role of Nickel in the Nickel-Palladium Bilayer for Electrocatalytic Oxidation of Ethanol in Alkaline Media. J. Phys. Chem. C 2014, 118 (39), 22473– 22478,  DOI: 10.1021/jp411601c
      32
      Enhancing Role of Nickel in the Nickel-Palladium Bilayer for Electrocatalytic Oxidation of Ethanol in Alkaline Media
      del Rosario, Julie Anne D.; Ocon, Joey D.; Jeon, Hongrae; Yi, Youngmi; Lee, Jae Kwang; Lee, Jaeyoung
      Journal of Physical Chemistry C (2014), 118 (39), 22473-22478CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      Direct ethanol fuel cells (DEFCs) have been widely studied because of their potential as a high-energy d. and low-toxicity power source of the future. Suitable catalysts for the anode reaction, however, are necessary to fully utilize the advantages of DEFCs. In this paper, we fabricated nickel (Ni)-palladium (Pd) bimetallic catalysts with a bilayer structure, using sputtering deposition on a titanium (Ti) foil substrate, and investigated the activity and stability of the catalysts toward ethanol electro-oxidn. in alk. media. Our results suggest that while Pd is the active component and Ni has negligible activity toward ethanol oxidn., Ni-modified Pd (NiPd/Ti) provides the best activity in comparison to PdNi/Ti and the monometallic catalysts. In fact, optimizing the Ni amt. could lead to a highly active and stable bimetallic electrocatalyst because of Ni's ability to increase the active surface area of the Pd layer, provide hydroxyl species to replenish the active sites, and act as a protective layer to the Pd. Overall, these results provide a better understanding on the role of Ni in bimetallic catalysts, esp. in a bilayer configuration, to allow the use of an ethanol oxidn. reaction (EOR)-active electrocatalyst with a much lower Pd content.
    33. 33
      White, J.; Peters, L.; Martín-Yerga, D.; Terekhina, I.; Anil, A.; Lundberg, H.; Johnsson, M.; Salazar-Alvarez, G.; Henriksson, G.; Cornell, A. Glycerol Electrooxidation at Industrially Relevant Current Densities Using Electrodeposited PdNi/Nifoam Catalysts in Aerated Alkaline Media. J. Electrochem. Soc. 2023, 170 (8), 086504,  DOI: 10.1149/1945-7111/acee27
      There is no corresponding record for this reference.
    34. 34
      Hiltrop, D.; Cychy, S.; Elumeeva, K.; Schuhmann, W.; Muhler, M. Spectroelectrochemical Studies on the Effect of Cations in the Alkaline Glycerol Oxidation Reaction over Carbon Nanotube-Supported Pd Nanoparticles. Beilstein J. Org. Chem. 2018, 14 (1), 1428– 1435,  DOI: 10.3762/bjoc.14.120
      34
      Spectroelectrochemical studies on the effect of cations in the alkaline glycerol oxidation reaction over carbon nanotube-supported Pd nanoparticles
      Hiltrop Dennis; Cychy Steffen; Muhler Martin; Elumeeva Karina; Schuhmann Wolfgang
      Beilstein journal of organic chemistry (2018), 14 (), 1428-1435 ISSN:1860-5397.
      The effects of the alkali cations Na(+) and K(+) were investigated in the alkaline electrochemical oxidation of glycerol over Pd nanoparticles (NPs) deposited on functionalized carbon nanotubes (CNTs). The electrocatalytic activity was assessed by cyclic voltammetry revealing a lower overpotential of glycerol oxidation for nitrogen-functionalized Pd/NCNTs compared with oxygen-functionalized Pd/OCNTs. Whereas significantly lower current densities were observed for Pd/OCNT in NaOH than in KOH in agreement with stronger non-covalent interactions on the Pd surface, Pd/NCNT achieved an approximately three-times higher current density in NaOH than in KOH. In situ electrochemistry/IR spectroscopy was applied to unravel the product distribution as a function of the applied potential in NaOH and KOH. The IR spectra exhibited strongly changing band patterns upon varying the potential between 0.77 and 1.17 V vs RHE: at low potentials oxidized C3 species such as mesoxalate and tartronate were formed predominantly, and with increasing potentials C2 and C1 species originating from C-C bond cleavage were identified. The tendency to produce carbonate was found to be less pronounced in KOH. The less favored formation of highly oxidized C3 species and of carbonate is deduced to be the origin of the lower current densities in the cyclic voltammograms (CVs) for Pd/NCNT in KOH. The enhanced current densities in NaOH are rationalized by the presence of Na(+) ions bound to the basic nitrogen species in the NCNT support. Adsorbed Na(+) ions can form complexes with the organic molecules, presumably enhanced by the chelate effect. In this way, the organic molecules are assumed to be bound more tightly to the NCNT support in close proximity to the Pd NPs facilitating their oxidation.
    35. 35
      Rahim, S. A. N. M.; Lee, C. S.; Abnisa, F.; Aroua, M. K.; Daud, W. A. W.; Cognet, P.; Pérès, Y. A Review of Recent Developments on Kinetics Parameters for Glycerol Electrochemical Conversion - A by-Product of Biodiesel. Sci. Total Environ. 2020, 705, 135137,  DOI: 10.1016/j.scitotenv.2019.135137
      35
      A review of recent developments on kinetics parameters for glycerol electrochemical conversion - A by-product of biodiesel
      Rahim, Siti Aqilah Nadhirah Md.; Lee, Ching Shya; Abnisa, Faisal; Aroua, Mohamed Kheireddine; Daud, Wan Ashri Wan; Cognet, Patrick; Peres, Yolande
      Science of the Total Environment (2020), 705 (), 135137CODEN: STENDL; ISSN:0048-9697. (Elsevier B.V.)
      A review. Glycerol is a byproduct produced from biodiesel, fatty acid, soap and bioethanol industries. Today, the value of glycerol is decreasing in the global market due to glycerol surplus, which primarily resulted from the speedy expansion of biodiesel producers around the world. Numerous studies proposed ways of managing and treating glycerol, as well as converting it into value-added compds. The electrochem. conversion method is preferred for this transformation due to its simplicity and hence, it is discussed. Addnl., the factors that could affect the process mechanisms and products distribution in the electrochem. process, including electrodes materials, pH of electrolyte, applied potential, c.d., temp. and additives are also thoroughly explained. Value-added compds. that can be produced from the electrochem. conversion of glycerol include glyceraldehyde, dihydroxyacetone, glycolic acid, glyceric acid, lactic acid, 1,2-propanediol, 1,3-propanediol, tartronic acid and mesoxalic acid. These compds. have broad applications in cosmetics, pharmaceutical, food and polymer industries are also described. This review will be devoted to a comprehensive overview of the current scenario in the glycerol electrochem. conversion, the factors affecting the mechanism pathways, reaction rates, product selectivity and yield. Possible outcomes obtained from the process and their benefits to the industries are discussed. The use of solid acid catalysts as additives for future studies is also suggested.
    36. 36
      Rodrigues, T. S.; Zhao, M.; Yang, T.-H.; Gilroy, K. D.; da Silva, A. G. M.; Camargo, P. H. C.; Xia, Y. Synthesis of Colloidal Metal Nanocrystals: A Comprehensive Review on the Reductants. Chem.─Eur. J. 2018, 24 (64), 16944– 16963,  DOI: 10.1002/chem.201802194
      36
      Synthesis of Colloidal Metal Nanocrystals: A Comprehensive Review on the Reductants
      Rodrigues, Thenner S.; Zhao, Ming; Yang, Tung-Han; Gilroy, Kyle D.; da Silva, Anderson G. M.; Camargo, Pedro H. C.; Xia, Younan
      Chemistry - A European Journal (2018), 24 (64), 16944-16963CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
      There is a growing interest in controlling the synthesis of colloidal metal nanocrystals and thus tailoring their properties toward various applications. In this context, choosing an appropriate combination of reagents (e.g., salt precursor, reductant, capping agent, and stabilizer) plays a pivotal role in enabling the synthesis of metal nanocrystals with diversified sizes, shapes, and structures. Here we present a comprehensive review that highlights one of the key reagents for the synthesis of metal nanocrystals via chem. redn.: the reductants. We start with a brief introduction to the compds. commonly employed as reductants in the colloidal synthesis of metal nanocrystals by showing their oxidn. half-reactions and the corresponding oxidn. potentials. Then we offer specific examples pertaining to the controlled synthesis of metal nanocrystals, followed by some fundamental aspects covering the general mechanisms of metal ion redn. based on the Marcus Theory. Afterwards, we present a case-by-case discussion on a wide variety of reductants, including their major properties, redn. mechanisms, and addnl. effects on the final products. We illustrate these aspects by selecting key examples from the literature and paying close attention to the underlying mechanism in each case. At the end, we conclude by summarizing the highlights of the review and providing some perspectives on future directions.
    37. 37
      Poerwoprajitno, A. R.; Gloag, L.; Cheong, S.; Gooding, J. J.; Tilley, R. D. Synthesis of Low- and High-Index Faceted Metal (Pt, Pd, Ru, Ir, Rh) Nanoparticles for Improved Activity and Stability in Electrocatalysis. Nanoscale 2019, 11 (41), 18995– 19011,  DOI: 10.1039/C9NR05802H
      37
      Synthesis of low- and high-index faceted metal (Pt, Pd, Ru, Ir, Rh) nanoparticles for improved activity and stability in electrocatalysis
      Poerwoprajitno, Agus R.; Gloag, Lucy; Cheong, Soshan; Gooding, J. Justin; Tilley, Richard D.
      Nanoscale (2019), 11 (41), 18995-19011CODEN: NANOHL; ISSN:2040-3372. (Royal Society of Chemistry)
      A review. Driven by the quest for future energy soln., faceted metal nanoparticles are being pursued as the next generation electrocatalysts for renewable energy applications. Thanks to recent advancement in soln. phase synthesis, different low- and high-index facets on metal nanocrystals become accessible and are tested for specific electrocatalytic reactions. This minireview summarises the key approaches to prep. nanocrystals contg. the most catalytically active platinum group metals (Pt, Pd, Ru, Ir and Rh) exposed with low- and high-index facets using soln. phase synthesis. Electrocatalytic studies related to the different facets are highlighted to emphasize the importance of exposing facets for catalyzing these reactions, namely oxygen redn. reaction (ORR), hydrogen oxidn. reaction (HOR), alc. oxidn. including methanol (MOR) and ethanol oxidn. reactions (EOR), formic acid oxidn. reaction (FAOR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). The future outlook discusses the challenges and opportunities for making electrocatalysts that are even more active and stable.
    38. 38
      Gilroy, K. D.; Ruditskiy, A.; Peng, H.-C.; Qin, D.; Xia, Y. Bimetallic Nanocrystals: Syntheses, Properties, and Applications. Chem. Rev. 2016, 116 (18), 10414– 10472,  DOI: 10.1021/acs.chemrev.6b00211
      38
      Bimetallic Nanocrystals: Syntheses, Properties, and Applications
      Gilroy, Kyle D.; Ruditskiy, Aleksey; Peng, Hsin-Chieh; Qin, Dong; Xia, Younan
      Chemical Reviews (Washington, DC, United States) (2016), 116 (18), 10414-10472CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      Achieving mastery over the synthesis of metal nanocrystals has emerged as one of the foremost scientific endeavors in recent years. This intense interest stems from the fact that the compn., size, and shape of nanocrystals not only define their overall physicochem. properties but also det. their effectiveness in technol. important applications. Our aim is to present a comprehensive review of recent research activities on bimetallic nanocrystals. We begin with a brief introduction to the architectural diversity of bimetallic nanocrystals, followed by discussion of the various synthetic techniques necessary for controlling the elemental ratio and spatial arrangement. We have selected key examples from the literature that exemplify crit. concepts and place a special emphasis on mechanistic understanding. We then discuss the compn.-dependent properties of bimetallic nanocrystals in terms of catalysis, optics, and magnetism and conclude the Review by highlighting applications that have been enabled and/or enhanced by precisely controlling the synthesis of bimetallic nanocrystals.
    39. 39
      Göksu, H.; Ho, S. F.; Metin, O. ̈.; Korkmaz, K.; Mendoza Garcia, A.; Gültekin, M. S.; Sun, S. Tandem Dehydrogenation of Ammonia Borane and Hydrogenation of Nitro/Nitrile Compounds Catalyzed by Graphene-Supported NiPd Alloy Nanoparticles. ACS Catal. 2014, 4 (6), 1777– 1782,  DOI: 10.1021/cs500167k
      39
      Tandem Dehydrogenation of Ammonia Borane and Hydrogenation of Nitro/Nitrile Compounds Catalyzed by Graphene-Supported NiPd Alloy Nanoparticles
      Goksu, Haydar; Ho, Sally Fae; Metin, Onder; Korkmaz, Katip; Mendoza Garcia, Adriana; Gultekin, Mehmet Serdar; Sun, Shouheng
      ACS Catalysis (2014), 4 (6), 1777-1782CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
      Nickel-palladium alloy nanoparticles supported on graphene were prepd. and used as catalysts for the chemoselective transfer hydrogenation reactions of nitro compds. and nitriles using ammonia-borane as the stoichiometric reductant. Of the graphene-supported nanoparticles prepd., the graphene-supported Ni30Pd70 nanoparticles were the most active. In the presence of graphene-supported Ni30Pd70 nanoparticles and ammonia-borane, aryl nitro compds., nitromethane, and nitroethane were hydrogenated to the corresponding amines in >99% yields and in 5-30 min at ambient temp. Aryl nitriles, propanenitrile, and isobutyronitrile were reduced to primary amines in 90->99% yields in 5-720 min at ambient temps.; nitro-substituted aryl nitriles were reduced chemoselectively to amino nitriles.
    40. 40
      Hummelgård, C.; Karlsson, R. K. B.; Bäckström, J.; Rahman, S. M. H.; Cornell, A.; Eriksson, S.; Olin, H. Physical and Electrochemical Properties of Cobalt Doped (Ti,Ru)O2 Electrode Coatings. Mater. Sci. Eng. B 2013, 178 (20), 1515– 1522,  DOI: 10.1016/j.mseb.2013.08.018
      There is no corresponding record for this reference.
    41. 41
      Bolzán, A. Phenomenological Aspects Related to the Electrochemical Behaviour of Smooth Palladium Electrodes in Alkaline Solutions. J. Electroanal. Chem. 1995, 380 (1–2), 127– 138,  DOI: 10.1016/0022-0728(94)03627-F
      41
      Phenomenological aspects related to the electrochemical behavior of smooth palladium electrodes in alkaline solutions
      Bolzan, A. E.
      Journal of Electroanalytical Chemistry (1995), 380 (1-2), 127-38CODEN: JECHES ISSN:. (Elsevier)
      The voltammetric behavior of smooth palladium electrodes in 1M NaOH was studied in the potential range related to the thermodn. stability of water. The electrosorption of H atoms on bulk Pd appears as a reversible reaction coupled to a diffusion process which occurs within bulk Pd. The voltammetric electrodesorption of H from bulk Pd is a process under mixed control, i.e. the diffusion from the bulk and the surface oxidn. of H atoms. Fast pseudocapacitive reactions are detected in the range 0.2-0.4 V assocd. with the adsorption of H atoms at the submonolayer level. The initial stages of Pd oxide layer formation, at ∼0.68 V, involves two reversible stages. The Pd oxide monolayer formation is achieved at 1.25 V/RHE and is followed by the formation of a 3rd reversible system. This system is enhanced by an excursion in the potential range of the oxygen evolution reaction. This reversible system is probably a redox system involving Pd(II)/Pd(IV) species. The voltammetric electroredn. of the Pd oxide film shows rather irreversible behavior. Inhibition effects on the reversible adsorption of H atoms due to residual oxide species were obsd. as well as inhibition on loading the Pd electrode with hydrogen to form the (α+β)-PdH phase. Rotating ring-disk expts. demonstrate that Pd electrodissoln. in basic solns. is much smaller than in acid solns. However, sol. palladium species are detected, esp. during the formation of the fast redox systems, in the potential range related to Pd oxide layer growth.
    42. 42
      Breiter, M. W. Dissolution and Adsorption of Hydrogen at Smooth Pd Wires of the Alpha Phase in Sulfuric Acid Solution. J. Electroanal. Chem. 1977, 81 (2), 275– 284,  DOI: 10.1016/S0022-0728(77)80023-5
      42
      Dissolution and adsorption of hydrogen at smooth palladium wires at potentials of the alpha phase in sulfuric acid solution
      Breiter, M. W.
      Journal of Electroanalytical Chemistry and Interfacial Electrochemistry (1977), 81 (2), 275-84CODEN: JEIEBC; ISSN:0022-0728.
      After decreasing the electrode potential rapidly from 0.7 V, H atoms were allowed to diffuse into Pd wires for 10 or 1 s at const. potential in the region of the α phase. Subsequently the anodic current due to H removal at 0.7 V was recorded by the oscilloscope. The current decays after a certain time according to a law characteristic for the diffusion of H from the interior of the Pd wire to the surface as rate-controlling process. The bulk concn. SCH of H atoms directly below the surface was computed on the basis of the diffusion process. The amt. QH of H adsorbed on the surface was detd. as the difference between the integral charge Q from the exptl. current-time curves and the integral charge Q' computed for the diffusion process within a suitable interval of time. The dependence of the bulk concn. SCH and of the H coverage QH upon potential were established and discussed.
    43. 43
      Chierchie, T.; Mayer, C.; Lorenz, W. J. Structural Changes of Surface Oxide Layers on Palladium. J. Electroanal. Chem. 1982, 135, 211– 220,  DOI: 10.1016/0368-1874(82)85121-6
      43
      Structural changes of surface oxide layers on palladium
      Chierchie, T.; Mayer, C.; Lorenz, W. J.
      Journal of Electroanalytical Chemistry and Interfacial Electrochemistry (1982), 135 (2), 211-20CODEN: JEIEBC; ISSN:0022-0728.
      The anodic formation of oxide layers on Pd and their cathodic redn. were investigated in HClO4 solns. using cyclic voltammetry and linear sweep polarization. The structure of the voltammograms depends on the anodic polarization and the polarization routine, but less on the sweep rate. From the measured cathodic charge amts. of the redn. as function of these parameters, it is assumed that slow structural changes of the oxide layer occur.
    44. 44
      Hjorth Larsen, A.; Jørgen Mortensen, J.; Blomqvist, J.; Castelli, I. E.; Christensen, R.; Dułak, M.; Friis, J.; Groves, M. N.; Hammer, B.; Hargus, C.; Hermes, E. D.; Jennings, P. C.; Bjerre Jensen, P.; Kermode, J.; Kitchin, J. R.; Leonhard Kolsbjerg, E.; Kubal, J.; Kaasbjerg, K.; Lysgaard, S.; Bergmann Maronsson, J.; Maxson, T.; Olsen, T.; Pastewka, L.; Peterson, A.; Rostgaard, C.; Schiøtz, J.; Schütt, O.; Strange, M.; Thygesen, K. S.; Vegge, T.; Vilhelmsen, L.; Walter, M.; Zeng, Z.; Jacobsen, K. W. The Atomic Simulation Environment-a Python Library for Working with Atoms. J. Phys.: Condens. Matter 2017, 29 (27), 273002,  DOI: 10.1088/1361-648X/aa680e
      44
      The atomic simulation environment-a Python library for working with atoms
      Hjorth Larsen Ask; Jorgen Mortensen Jens; Blomqvist Jakob; Castelli Ivano E; Christensen Rune; Dulak Marcin; Friis Jesper; Groves Michael N; Hammer Bjork; Hargus Cory; Hermes Eric D; Jennings Paul C; Bjerre Jensen Peter; Kermode James; Kitchin John R; Leonhard Kolsbjerg Esben; Kubal Joseph; Kaasbjerg Kristen; Lysgaard Steen; Bergmann Maronsson Jon; Maxson Tristan; Olsen Thomas; Pastewka Lars; Peterson Andrew; Rostgaard Carsten; Schiotz Jakob; Schutt Ole; Strange Mikkel; Thygesen Kristian S; Vegge Tejs; Vilhelmsen Lasse; Walter Michael; Zeng Zhenhua; Jacobsen Karsten W
      Journal of physics. Condensed matter : an Institute of Physics journal (2017), 29 (27), 273002 ISSN:.
      The atomic simulation environment (ASE) is a software package written in the Python programming language with the aim of setting up, steering, and analyzing atomistic simulations. In ASE, tasks are fully scripted in Python. The powerful syntax of Python combined with the NumPy array library make it possible to perform very complex simulation tasks. For example, a sequence of calculations may be performed with the use of a simple 'for-loop' construction. Calculations of energy, forces, stresses and other quantities are performed through interfaces to many external electronic structure codes or force fields using a uniform interface. On top of this calculator interface, ASE provides modules for performing many standard simulation tasks such as structure optimization, molecular dynamics, handling of constraints and performing nudged elastic band calculations.
    45. 45
      Kresse, G.; Furthmüller, J. Efficient Iterative Schemes for Ab Initio Total-Energy Calculations Using a Plane-Wave Basis Set. Phys. Rev. B 1996, 54 (16), 11169– 11186,  DOI: 10.1103/PhysRevB.54.11169
      45
      Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set
      Kresse, G.; Furthmueller, J.
      Physical Review B: Condensed Matter (1996), 54 (16), 11169-11186CODEN: PRBMDO; ISSN:0163-1829. (American Physical Society)
      The authors present an efficient scheme for calcg. the Kohn-Sham ground state of metallic systems using pseudopotentials and a plane-wave basis set. In the first part the application of Pulay's DIIS method (direct inversion in the iterative subspace) to the iterative diagonalization of large matrixes will be discussed. This approach is stable, reliable, and minimizes the no. of order Natoms3 operations. In the second part, we will discuss an efficient mixing scheme also based on Pulay's scheme. A special "metric" and a special "preconditioning" optimized for a plane-wave basis set will be introduced. Scaling of the method will be discussed in detail for non-self-consistent and self-consistent calcns. It will be shown that the no. of iterations required to obtain a specific precision is almost independent of the system size. Altogether an order Natoms2 scaling is found for systems contg. up to 1000 electrons. If we take into account that the no. of k points can be decreased linearly with the system size, the overall scaling can approach Natoms. They have implemented these algorithms within a powerful package called VASP (Vienna ab initio simulation package). The program and the techniques have been used successfully for a large no. of different systems (liq. and amorphous semiconductors, liq. simple and transition metals, metallic and semiconducting surfaces, phonons in simple metals, transition metals, and semiconductors) and turned out to be very reliable.
    46. 46
      Wellendorff, J.; Lundgaard, K. T.; Møgelhøj, A.; Petzold, V.; Landis, D. D.; Nørskov, J. K.; Bligaard, T.; Jacobsen, K. W. Density Functionals for Surface Science: Exchange-Correlation Model Development with Bayesian Error Estimation. Phys. Rev. B 2012, 85 (23), 235149,  DOI: 10.1103/PhysRevB.85.235149
      46
      Density functionals for surface science: exchange-correlation model development with Bayesian error estimation
      Wellendorff, Jess; Lundgaard, Keld T.; Moegelhoej, Andreas; Petzold, Vivien; Landis, David D.; Noerskov, Jens K.; Bligaard, Thomas; Jacobsen, Karsten W.
      Physical Review B: Condensed Matter and Materials Physics (2012), 85 (23), 235149/1-235149/23CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
      A methodol. for semiempirical d. functional optimization, using regularization and cross-validation methods from machine learning, is developed. We demonstrate that such methods enable well-behaved exchange-correlation approxns. in very flexible model spaces, thus avoiding the overfitting found when std. least-squares methods are applied to high-order polynomial expansions. A general-purpose d. functional for surface science and catalysis studies should accurately describe bond breaking and formation in chem., solid state physics, and surface chem., and should preferably also include van der Waals dispersion interactions. Such a functional necessarily compromises between describing fundamentally different types of interactions, making transferability of the d. functional approxn. a key issue. We investigate this trade-off between describing the energetics of intramol. and intermol., bulk solid, and surface chem. bonding, and the developed optimization method explicitly handles making the compromise based on the directions in model space favored by different materials properties. The approach is applied to designing the Bayesian error estn. functional with van der Waals correlation (BEEF-vdW), a semilocal approxn. with an addnl. nonlocal correlation term. Furthermore, an ensemble of functionals around BEEF-vdW comes out naturally, offering an est. of the computational error. An extensive assessment on a range of data sets validates the applicability of BEEF-vdW to studies in chem. and condensed matter physics. Applications of the approxn. and its Bayesian ensemble error est. to two intricate surface science problems support this.
    47. 47
      Anil, A.; White, J.; Campos dos Santos, E.; Terekhina, I.; Johnsson, M.; Pettersson, L. G. M.; Cornell, A.; Salazar-Alvarez, G. Effect of Pore Mesostructure on the Electrooxidation of Glycerol on Pt Mesoporous Catalysts. J. Mater. Chem. A 2023, 11 (31), 16570– 16577,  DOI: 10.1039/D3TA01738A
      47
      Effect of pore mesostructure on the electrooxidation of glycerol on Pt mesoporous catalysts
      Anil, Athira; White, Jai; Campos dos Santos, Egon; Terekhina, Irina; Johnsson, Mats; Pettersson, Lars G. M.; Cornell, Ann; Salazar-Alvarez, German
      Journal of Materials Chemistry A: Materials for Energy and Sustainability (2023), 11 (31), 16570-16577CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
      Glycerol is a renewable chem. that has become widely available and inexpensive owing to the increased prodn. of biodiesel. Noble metal materials are effective catalysts for the prodn. of hydrogen and value-added products through the electrooxidn. of glycerol. In this study, we developed three platinum systems with distinct pore mesostructures, e.g., hierarchical pores (HP), cubic pores (CP) and linear pores (LP), all with high electrochem. active surface area (ECSA). The ECSA-normalized GEOR catalytic activity of the systems follows HPC > LPC > CPC > com. Pt/C. Regarding the oxidn. products, we observe glyceric acid as the main three-carbon product (C3), with oxalic acids as the main two-carbon oxidn. product. DFT-based theor. calcns. support the glyceraldehyde route going through tartronic acid toward oxalic acid and also help in understanding why the dihydroxyacetone (DHA) route is active despite the absence of DHA amongst the obsd. oxidn. products.
    48. 48
      dos Santos, E. C.; Araujo, R. B.; Valter, M.; Salazar-Alvarez, G.; Johnsson, M.; Bajdich, M.; Abild-Pedersen, F.; Pettersson, L. G. M. Efficient Screening of Bi-Metallic Electrocatalysts for Glycerol Valorization. Electrochim. Acta 2021, 398, 139283,  DOI: 10.1016/j.electacta.2021.139283
      48
      Efficient Screening of Bi-Metallic Electrocatalysts for Glycerol Valorization
      dos Santos, Egon Campos; Araujo, Rafael B.; Valter, Mikael; Salazar-Alvarez, German; Johnsson, Mats; Bajdich, Michal; Abild-Pedersen, Frank; Pettersson, Lars Gunnar Moody
      Electrochimica Acta (2021), 398 (), 139283CODEN: ELCAAV; ISSN:0013-4686. (Elsevier Ltd.)
      Glycerol is a byproduct of biodiesel prodn. and, as such, it is of limited economic value. By electrooxidn., glycerol can be used as a feedstock for scalable H prodn., in addn. to conversion to value-added products. The development of novel and efficient catalytic electrode materials for the anodic side of the reaction is a key towards a H-based energy economy. A computational screening protocol combining DFT, scaling relations, and microkinetic modeling allows for a rational selection of novel catalysts that can deliver efficient glycerol electrooxidn., low cost of prodn., and environmental sustainability. Activity and chem. selectivity towards H prodn. on pure metal catalysts is discussed in terms of volcano-shaped plots. The selectivity in the glycerol oxidn. reaction is influenced by a different energy landscape when in the presence of H2O and best classified by a comparison of O-H and C-H bond-breaking barriers. The authors screened 3570 bi-metallic catalysts in the AB (L10) and A3B (L12) ordered structures for activity, stability, price, and toxicity. By filtering based on the criteria for toxicity, resistance to oxidn., miscibility, and price, the authors have identified 5 L10 structured catalysts (AgPd, AuPd, PtSb, CuPt, and AgPt) and 20 L12 catalysts (Ga3Ta, In3Ta, Ir3W, Ir3Mo, Cu3Pt, Ir3Ta, Ir3Re, Pd3Bi, Pd3Cu, Pd3W, Pd3Co, Pd3Sn, Pd3Mo, Pd3Ag, Pd3Ga, Pd3Ta, Au3Ru, Pd3In, Au3Ir, and Pd3Au) that are all predicted to show high activity. The authors also identify an addnl. 37 L10 and 92 L12 structured electrocatalysts with an anticipated medium-high activity.
    49. 49
      T. C., Allison. NIST-JANAF Thermochemical Tables - SRD 13, 2013.  DOI: 10.18434/T42S31 .
      There is no corresponding record for this reference.
    50. 50
      Mathew, K.; Sundararaman, R.; Letchworth-Weaver, K.; Arias, T. A.; Hennig, R. G. Implicit Solvation Model for Density-Functional Study of Nanocrystal Surfaces and Reaction Pathways. J. Chem. Phys. 2014, 140 (8), 084106,  DOI: 10.1063/1.4865107
      50
      Implicit solvation model for density-functional study of nanocrystal surfaces and reaction pathways
      Mathew, Kiran; Sundararaman, Ravishankar; Letchworth-Weaver, Kendra; Arias, T. A.; Hennig, Richard G.
      Journal of Chemical Physics (2014), 140 (8), 084106/1-084106/8CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
      Solid-liq. interfaces are at the heart of many modern-day technologies and provide a challenge to many materials simulation methods. A realistic first-principles computational study of such systems entails the inclusion of solvent effects. We implement an implicit solvation model that has a firm theor. foundation into the widely used d.-functional code Vienna ab initio Software Package. The implicit solvation model follows the framework of joint d. functional theory. We describe the framework, our algorithm and implementation, and benchmarks for small mol. systems. We apply the solvation model to study the surface energies of different facets of semiconducting and metallic nanocrystals and the SN2 reaction pathway. Solvation reduces the surface energies of the nanocrystals, esp. for the semiconducting ones and increases the energy barrier of the SN2 reaction. (c) 2014 American Institute of Physics.
    51. 51
      Nørskov, J. K.; Rossmeisl, J.; Logadottir, A.; Lindqvist, L.; Kitchin, J. R.; Bligaard, T.; Jónsson, H. Origin of the Overpotential for Oxygen Reduction at a Fuel-Cell Cathode. J. Phys. Chem. B 2004, 108 (46), 17886– 17892,  DOI: 10.1021/jp047349j
      51
      Origin of the Overpotential for Oxygen Reduction at a Fuel-Cell Cathode
      Norskov, J. K.; Rossmeisl, J.; Logadottir, A.; Lindqvist, L.; Kitchin, J. R.; Bligaard, T.; Jonsson, H.
      Journal of Physical Chemistry B (2004), 108 (46), 17886-17892CODEN: JPCBFK; ISSN:1520-6106. (American Chemical Society)
      A method to obtain the stability of reaction intermediates of electrochem. processes using electronic structure calcns. is presented. This method is used in combination with detailed d. functional calcns. to develop a detailed description of the free-energy landscape of the electrochem. O redn. reaction over Pt(111), as a function of applied bias. This allowed identification of the origin of the overpotential of this reaction. Adsorbed O and hydroxyl are stable intermediates at potentials close to equil., and the calcd. rate const. for the activated p/electron transfer to adsorbed O or hydroxyl can account quant. for the obsd. kinetics. From a database of calcd. O and hydroxyl adsorption energies, the trends in the O redn. rate for a large no. of different transition and noble metals can be explained. Alternative reaction mechanisms involving p/electron transfer to adsorbed mol. O were also considered, and this peroxide mechanism dominates for most noble metals. The model suggests ways to improve the electrocatalytic properties of fuel cell cathodes.
    52. 52
      Sen, B.; Kuzu, S.; Demir, E.; Yıldırır, E.; Sen, F. Highly Efficient Catalytic Dehydrogenation of Dimethyl Ammonia Borane via Monodisperse Palladium-Nickel Alloy Nanoparticles Assembled on PEDOT. Int. J. Hydrogen Energy 2017, 42 (36), 23307– 23314,  DOI: 10.1016/j.ijhydene.2017.05.115
      52
      Highly efficient catalytic dehydrogenation of dimethyl ammonia borane via monodisperse palladium-nickel alloy nanoparticles assembled on PEDOT
      Sen, Betul; Kuzu, Sultan; Demir, Enes; Yildirir, Eyup; Sen, Fatih
      International Journal of Hydrogen Energy (2017), 42 (36), 23307-23314CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
      Addressed herein, the synthesis of the monodisperse poly(3,4-ethylenedioxythiophene)(PEDOT) supported palladium-nickel nanomaterials (3.32 ± 0.36 nm) and their applications as a catalyst in dimethylamine-borane (DMAB) dehydrogenation is outlined. Microwave assistance procedure was used in prepn. of nanomaterials where palladium and cobalt cations were reduced in PEDOT soln. (Pd-Ni@PEDOT) in microwave conditions. The characterization of the nanocatalyst was performed by using UV-VIS, XRD, XPS, TEM and HR-TEM-EELS analyses. The Pd-Ni@PEDOT NPs were found to be highly effective and stable for the dehydrogenation of DMAB. The catalytic activity of Pd-Ni@PEDOT was one of the highest one among the all prepd. catalysts in literature even at lower temps. and concns., yielding to give high turnover frequency (451.2 h-1) and low Ea (50.78 ± 2 kJ/mol) for dehydrocoupling of DMAB.
    53. 53
      Matin, M. A.; Jang, J.-H.; Kwon, Y.-U. PdM Nanoparticles (M = Ni, Co, Fe, Mn) with High Activity and Stability in Formic Acid Oxidation Synthesized by Sonochemical Reactions. J. Power Sources 2014, 262, 356– 363,  DOI: 10.1016/j.jpowsour.2014.03.109
      53
      PdM nanoparticles (M = Ni, Co, Fe, Mn) with high activity and stability in formic acid oxidation synthesized by sonochemical reactions
      Matin, Md. Abdul; Jang, Ji-Hoon; Kwon, Young-Uk
      Journal of Power Sources (2014), 262 (), 356-363CODEN: JPSODZ; ISSN:0378-7753. (Elsevier B.V.)
      Bimetallic alloy PdnM (n = 1 for M = Mn, Fe, and Co; n = 1, 2, and 3 for M = Ni) nanoparticles (NPs) are synthesized on carbon supports by sonochem. reactions of Pd(acac)2 (acac = acetylacetonate) with M(acac)2 (M = Ni, Co, Mn) or Fe(acac)3 in ethylene glycol. The NPs are characterized by powder X-ray diffractometry, transmission electron microscopy (TEM), and inductively coupled plasma-at. emission spectroscopy to det. their crystal structures, particle sizes, morphol., and elemental compns. Alloy formation of the NPs is proven by energy dispersive X-ray spectroscopy line profiles using scanning TEM. The electronic structures and the surface compns. of NPs are analyzed using XPS and Fourier-transform IR spectroscopy, resp. PdnM NPs are applied as electrocatalysts for formic acid oxidn. The incorporation of M in Pd reduces the poisoning by surface hydroxyl groups. Activities based on the current densities are in the order of PdNi > PdFe > PdCo > PdMn. Within the PdnNi series, the activity is in the order of PdNi > Pd2Ni > Pd3Ni. The PdnM NP electrocatalysts show higher activity by a factor of 2-3.5 and improved durability than similarly prepd. Pd NP electrocatalyst.
    54. 54
      Khan, M. S.; Khattak, R.; Khan, A.; Chen, Q.; Nisar, J.; Iqbal, Z.; Rashid, A.; Kamran, A. W.; Zekker, I.; Zahoor, M.; Alzahrani, K. J.; Batiha, G. E.-S. Synthesis and Characterizations of PdNi Carbon Supported Nanomaterials: Studies of Electrocatalytic Activity for Oxygen Reduction in Alkaline Medium. Molecules 2021, 26 (11), 3440,  DOI: 10.3390/molecules26113440
      54
      Synthesis and characterizations of PdNi carbon supported nanomaterials: studies of electrocatalytic activity for oxygen reduction in alkaline medium
      Khan, Muhammad Sufaid; Khattak, Rozina; Khan, Abbas; Chen, Qiuling; Nisar, Jan; Iqbal, Zahoor; Rashid, Abdur; Abdul Waheed Kamran; Zekker, Ivar; Zahoor, Muhammad; Alzahrani, Khalid J.; El-Saber Batiha, Gaber
      Molecules (2021), 26 (11), 3440CODEN: MOLEFW; ISSN:1420-3049. (MDPI AG)
      Electrocatalytic materials offer numerous benefits due to their wide range of applications. In this study, a polyol technique was used to synthesize PdNi nanoparticles (NPs) with different percent at. compns. (Pd = 50 to 90%) to explore their catalytic efficiency. The produced nanoparticles were characterized using X-ray diffraction (XRD) and electrochem. investigations. According to XRD measurements, the synthesized NPs were cryst. in nature, with crystallite sizes of about 2 nm. The electrochem. properties of the synthesized NPs were studied in alk. soln. through a rotating ring-disk electrode (RRDE) technique of cyclic voltammetry. The PdNi nanoparticles supported on carbon (PdNi/C) were used as electrocatalysts and their activity and stability were compared with the homemade Pd/C and Pt/C. In alk. soln., PdNi/C electrocatalysts showed improved oxygen redn. catalytic activity over benchmark Pd/C and Pt/C electrocatalysts in all compn. ratios. Furthermore, stability expts. revealed that PdNi 50:50 is more stable in alk. soln. than pure Pd and other PdNi compns.
    55. 55
      Wang, L.; Dong, K. J.; Wang, C. C.; Zou, R. P.; Zhou, Z. Y.; Yu, A. B. Computer Simulation of the Packing of Nanoparticles. Powder Technol. 2022, 401, 117317,  DOI: 10.1016/j.powtec.2022.117317
      55
      Computer simulation of the packing of nanoparticles
      Wang, L.; Dong, K. J.; Wang, C. C.; Zou, R. P.; Zhou, Z. Y.; Yu, A. B.
      Powder Technology (2022), 401 (), 117317CODEN: POTEBX; ISSN:0032-5910. (Elsevier B.V.)
      The packing of nanoparticles down to 20 nm is simulated by the discrete element method (DEM). The model is validated by good agreement between the simulated and measured porosity. It is found that the previous relationship between porosity and the force ratio of cohesion to gravity can also be applied to the packing of nanoparticles. However, different from microparticles, nanoparticle packing begins with agglomeration and then the agglomerates are packed together. The resulting packing structure is thus more like chains of agglomerates. The agglomeration process becomes more dominant when particle size decreases. Due to agglomeration, the packing structure of nanoparticles is found to be more sensitive to the initial porosity than that of microparticles, and the effects are analyzed in terms of the temporal evolution of agglomerates. The fractal anal. indicates that the agglomerates are fractal-like while the whole packing is not fractal-like. The packing structure can be characterized by the radial distribution function and coordination no. The results indicate that for nanoparticles, with decreasing particle size, local packing structure becomes denser although the overall porosity increases, which is different from that of microparticles. The results link the packing of particles at different scales, from macro to nano, while also reveal the crit. difference between the packing of nanoparticles and that of other particles.
    56. 56
      Eldridge, M. D.; Madden, P. A.; Frenkel, D. Entropy-Driven Formation of a Superlattice in a Hard-Sphere Binary Mixture. Nature 1993, 365 (6441), 35– 37,  DOI: 10.1038/365035a0
      56
      Entropy-driven formation of a superlattice in a hard-sphere binary mixture
      Eldridge, M. D.; Madden, P. A.; Frenkel, D.
      Nature (London, United Kingdom) (1993), 365 (6441), 35-7CODEN: NATUAS; ISSN:0028-0836.
      The possibility that the formation of an AB13 superlattice might be supported by entropy effects alone was investigated by computer simulations of a binary mixt. of hard spheres. Calcns. show that entropy alone is sufficient to stabilize the AB13 phase. and that the full phase diagram of this system is surprisingly complex. The results also suggest that vitrification or slow crystal nucleation in exptl. studies of colloidal hard spheres can prevent the formation of equil. phases.
    57. 57
      Wang, Z.; Schliehe, C.; Bian, K.; Dale, D.; Bassett, W. A.; Hanrath, T.; Klinke, C.; Weller, H. Correlating Superlattice Polymorphs to Internanoparticle Distance, Packing Density, and Surface Lattice in Assemblies of PbS Nanoparticles. Nano Lett. 2013, 13 (3), 1303– 1311,  DOI: 10.1021/nl400084k
      57
      Correlating Superlattice Polymorphs to Internanoparticle Distance, Packing Density, and Surface Lattice in Assemblies of PbS Nanoparticles
      Wang, Zhongwu; Schliehe, Constanze; Bian, Kaifu; Dale, Darren; Bassett, William A.; Hanrath, Tobias; Klinke, Christian; Weller, Horst
      Nano Letters (2013), 13 (3), 1303-1311CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)
      Assemblies of 3.5 nm PbS nanoparticles (NPs) nucleate in three dominant superlattice polymorphs: amorphous, bcc. and fcc. phase. This superlattice relation can be controlled by the inter-NP distance without changing the NP size. Upon increase of inter-NP distance, the packing d. decreases, and the capping mols. at NP surfaces change in structure and accordingly modify the surface energy. The driving force for NP assembly develops from an entropic maximization to a redn. of total free energy through multiple interactions between surface mols. and NPs and resulting variation of surface mols. Upon long-term aging and addnl. thermal treatment, fcc. undergoes a tetragonal distortion and subsequently transforms to bcc. phase, and simultaneously, the NPs embedded in supercrystals reduce surface energy primarily in {200} facets. Linking mol.-NP interactions with changes of packing d. and surface lattice spacings of NPs allows for an interpretation of principles governing the nucleation, structure stability, and transformation of PbS NP-assembled supercrystals.
    58. 58
      Bouju, X.; Duguet, É.; Gauffre, F.; Henry, C. R.; Kahn, M. L.; Mélinon, P.; Ravaine, S. Nonisotropic Self-Assembly of Nanoparticles: From Compact Packing to Functional Aggregates. Adv. Mater. 2018, 30 (27), 1706558,  DOI: 10.1002/adma.201706558
      There is no corresponding record for this reference.
    59. 59
      Wang, L.; Lavacchi, A.; Bellini, M.; D’Acapito, F.; Benedetto, F. D.; Innocenti, M.; Miller, H. A.; Montegrossi, G.; Zafferoni, C.; Vizza, F. Deactivation of Palladium Electrocatalysts for Alcohols Oxidation in Basic Electrolytes. Electrochim. Acta 2015, 177, 100– 106,  DOI: 10.1016/j.electacta.2015.02.026
      59
      Deactivation of Palladium Electrocatalysts for Alcohols Oxidation in Basic Electrolytes
      Wang, Lianqin; Lavacchi, Alessandro; Bellini, Marco; D'Acapito, Francesco; Benedetto, Francesco Di; Innocenti, Massimo; Miller, Hamish A.; Montegrossi, Giordano; Zafferoni, Claudio; Vizza, Francesco
      Electrochimica Acta (2015), 177 (), 100-106CODEN: ELCAAV; ISSN:0013-4686. (Elsevier Ltd.)
      Deactivation is one the main causes still preventing the full exploitation of Pd electrocatalysts in alk. direct alc. fuel cells and the electrochem. reforming of alcs. While often attributed to the adsorption of poisoning species generated in the alcs. oxidn., deactivation is provoked by the formation of Pd oxides. A combined approach including (i) fuel cell runs, (ii) cyclic voltammetry and (iii) near edge x-ray absorption spectroscopy has enabled the authors to draw the conclusions reported.
    60. 60
      Daily Metal Price: Palladium Price (USD/Gram) Chart for the Last Week. https://www.dailymetalprice.com/metalpricecharts.php?c=pd&u=oz&d=240 (accessed 10 16, 2023).
      There is no corresponding record for this reference.
    61. 61
      Daily Metal Price: Nickel Price (USD/Gram) Chart for the Last Week. https://www.dailymetalprice.com/metalpricecharts.php?c=ni&u=lb&d=0 (accessed 10 16, 2023).
      There is no corresponding record for this reference.
    62. 62
      Oliveira, V. L.; Morais, C.; Servat, K.; Napporn, T. W.; Tremiliosi-Filho, G.; Kokoh, K. B. Glycerol Oxidation on Nickel Based Nanocatalysts in Alkaline Medium - Identification of the Reaction Products. J. Electroanal. Chem. 2013, 703, 56,  DOI: 10.1016/j.jelechem.2013.05.021
      62
      Glycerol oxidation on nickel based nanocatalysts in alkaline medium - Identification of the reaction products
      Oliveira, V. L.; Morais, C.; Servat, K.; Napporn, T. W.; Tremiliosi-Filho, G.; Kokoh, K. B.
      Journal of Electroanalytical Chemistry (2013), 703 (), 56-62CODEN: JECHES; ISSN:1873-2569. (Elsevier B.V.)
      Carbon-supported Ni-based nanoparticles were prepd. by the impregnation method and used as anode electrocatalysts for glycerol conversion. These metallic powders were mixed with a suitable amt. of a Nafion/water soln. to make catalytic inks which were then deposited onto the surface of C Toray used as a conductive substrate. Long-term electrolyzes of glycerol were carried out in alk. medium by chronoamperometry expts. Anal. of the oxidn. products was performed with ion-exclusion liq. chromatog. which separates the analytes by ascending pKa. The spectroscopic measurements showed that the Co content in the anode compn. did contribute to the CC bond cleavage of the initial mol. of glycerol.
    63. 63
      Goetz, M. K.; Bender, M. T.; Choi, K.-S. Predictive Control of Selective Secondary Alcohol Oxidation of Glycerol on NiOOH. Nat. Commun. 2022, 13 (1), 5848,  DOI: 10.1038/s41467-022-33637-7
      63
      Predictive control of selective secondary alcohol oxidation of glycerol on NiOOH
      Goetz, McKenna K.; Bender, Michael T.; Choi, Kyoung-Shin
      Nature Communications (2022), 13 (1), 5848CODEN: NCAOBW; ISSN:2041-1723. (Nature Portfolio)
      Many biomass intermediates are polyols and selectively oxidizing only a primary or secondary alc. group is beneficial for the valorization of these intermediates. For example, prodn. of 1,3-dihydroxyacetone, a highly valuable oxidn. product of glycerol, requires selective secondary alc. oxidn. However, selective secondary alc. oxidn. is challenging due to its steric disadvantage. This study demonstrates that NiOOH, which oxidizes alcs. via two dehydrogenation mechanisms, hydrogen atom transfer and hydride transfer, can convert glycerol to 1,3-dihydroxyacetone with high selectivity when the conditions are controlled to promote hydrogen atom transfer, favoring secondary alc. oxidn. This rational prodn. of 1,3-dihydroxyacetone achieved by selectively enabling one desired dehydrogenation pathway, without requiring alteration of catalyst compn., demonstrates how comprehensive mechanistic understanding can enable predictive control over selectivity.
    64. 64
      Zhang, N.; Wang, J.; Zhang, W.; Zhao, Y.; Dong, Z.; Wu, Z.; Xu, G.-R.; Wang, L. Self-Supported PdNi Dendrite on Ni Foam for Improving Monohydric Alcohol and Polyhydric Alcohols Electrooxidation. Fuel 2022, 326, 125083,  DOI: 10.1016/j.fuel.2022.125083
      64
      Self-supported PdNi dendrite on Ni foam for improving monohydric alcohol and polyhydric alcohols electrooxidation
      Zhang, Ning; Wang, Jing; Zhang, Wen; Zhao, Yingxiu; Dong, Zemeng; Wu, Zexing; Xu, Guang-Rui; Wang, Lei
      Fuel (2022), 326 (), 125083CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
      Despite considerable efforts to study direct alc. fuel cells (DAFCs), the development of efficient bifunctional catalysts for monohydric alc. and polyhydric alcs. remains a great challenge. This work reports the prepn. of self-supported PdNi dendrites on Ni foam (self-supported PdNi DNTs/NF) with a large sp. surface area by a simple self-sacrificing template and hydrothermal method. The presence of NF with enrichment of nucleation sites is crucial for the generation of self-supported PdNi DNTs. The as-obtained self-supported PdNi DNTs/NF exhibits an excellent property for ethanol and glycerol electrooxidn. with the mass activity of 2375.7 mA mg-1cat and 2451.6 mA mg-1cat, the specific activity of 10.07 mA cm-2 and 10.84 mA cm-2, resp., in alk. media, which should attribute to abundant high-index facets and low-coordinated atoms on the edge of branches. Furthermore, the PdNi DNTs/NF exhibits outstanding long-term durability in the current-time test for 7200 s with superior anti-CO poisoning performance, possessing a potential application in DAFCs.
    65. 65
      Luo, H.; Yukuhiro, V. Y.; Fernández, P. S.; Feng, J.; Thompson, P.; Rao, R. R.; Cai, R.; Favero, S.; Haigh, S. J.; Durrant, J. R.; Stephens, I. E. L.; Titirici, M.-M. Role of Ni in PtNi Bimetallic Electrocatalysts for Hydrogen and Value-Added Chemicals Coproduction via Glycerol Electrooxidation. ACS Catal. 2022, 12 (23), 14492– 14506,  DOI: 10.1021/acscatal.2c03907
      65
      Role of nickel in platinum nickel bimetallic electrocatalysts for hydrogen and value-added chemicals coproduction through glycerol electrooxidation
      Luo, Hui; Yukuhiro, Victor Y.; Fernandez, Pablo S.; Feng, Jingyu; Thompson, Paul; Rao, Reshma R.; Cai, Rongsheng; Favero, Silvia; Haigh, Sarah J.; Durrant, James R.; Stephens, Ifan E. L.; Titirici, Maria-Magdalena
      ACS Catalysis (2022), 12 (23), 14492-14506CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
      Pt-based bimetallic electrocatalysts are promising candidates to convert surplus glycerol from the biodiesel industry to value-added chems. and coproduce hydrogen. It is expected that the nature and content of the elements in the bimetallic catalyst can not only affect the reaction kinetics but also influence the product selectivity, providing a way to increase the yield of the desired products. Hence, in this work, we investigate the electrochem. oxidn. of glycerol on a series of PtNi nanoparticles with increasing Ni content using a combination of physicochem. structural anal., electrochem. measurements, operando spectroscopic techniques, and advanced product characterizations. With a moderate Ni content and a homogenously alloyed bimetallic Pt-Ni structure, the PtNi2 catalyst displayed the highest reaction activity among all materials studied in this work. In situ FTIR data show that PtNi2 can activate the glycerol mol. at a more neg. potential (0.4 VRHE) than the other PtNi catalysts. In addn., its surface can effectively catalyze the complete C-C bond cleavage, resulting in lower CO poisoning and higher stability. Operando X-ray absorption spectroscopy and UV-vis spectroscopy suggest that glycerol adsorbs strongly onto surface Ni(OH)x sites, preventing their oxidn. and activation of oxygen or hydroxyl from water. As such, we propose that the role of Ni in PtNi toward glycerol oxidn. is to tailor the electronic structure of the pure Pt sites rather than a bifunctional mechanism. Our expts. provide guidance for the development of bimetallic catalysts toward highly efficient, selective, and stable glycerol oxidn. reactions.
    66. 66
      Mphahlele, N. E.; Ipadeola, A. K.; Haruna, A. B.; Mwonga, P. V.; Modibedi, R. M.; Palaniyandy, N.; Billing, C.; Ozoemena, K. I. Microwave-induced Defective PdFe/C Nano-electrocatalyst for Highly Efficient Alkaline Glycerol Oxidation Reactions. Electrochim. Acta 2022, 409, 139977,  DOI: 10.1016/j.electacta.2022.139977
      66
      Microwave-induced defective PdFe/C nano-electrocatalyst for highly efficient alkaline glycerol oxidation reactions
      Mphahlele, Nonhlanhla Eugenia; Ipadeola, Adewale Kabir; Haruna, Aderemi Bashiru; Mwonga, Patrick Vaati; Modibedi, Remegia Mmalewane; Palaniyandy, Nithyadharseni; Billing, Caren; Ozoemena, Kenneth Ikechukwu
      Electrochimica Acta (2022), 409 (), 139977CODEN: ELCAAV; ISSN:0013-4686. (Elsevier Ltd.)
      Pd-based mono- and bi-metallic nano-electrocatalysts (Pd/C and PdFe/C) have been synthesized using two different methods for comparison: conventional sodium borohydride (NaBH4) route and microwave-assisted redn. process. The performance of the nano-electrocatalysts is tested for glycerol oxidn. reaction (GlyOR) in an alk. medium. DFT simulation proves that incorporation of Fe to Pd(111) leads to an increased partial d. of states (PDOS) compared to Pd alone, confirming the importance for bimetallic nano-electrocatalyst. The adsorption energy of glycerol onto PdFe is slightly weaker (A.E. = -48.89 eV) than the Pd alone (A.E. = -48.60 eV), indicating the ease with which glycerol can be generated at the PdFe surface than at the Pd alone. XRD show that microwave-irradiated samples (Pd(MW) and PdFe(MW)) are more cryst. than the conventional Pd and PdFe. TEM images show that the Pd(MW) and PdFe(MW) have slightly larger particle sizes (5.30 - 7.40 nm) than those from the conventional route (2.48 - 3.02 nm). Nitrogen adsorption-desorption anal. shows that the microwave samples exhibit slightly larger surface area compared to samples from NaBH4 route. Raman and XPS show that Pd(MW) and PdFe(MW) are more prone to defects (i.e., oxygen vacancies) compared to the NaBH4 route. The microwave samples gave the highest electrocatalytic properties toward glycerol than the NaBH4 route (including high electrochem. active surface area, high c.d. response, high resistance to poisoning due to carbonaceous intermediates arising from the GlyOR, and high cond. or low interfacial resistance) compared to samples from the conventional NaBH4 method. The findings in this work go a long way to understanding the physico-chem. and electrochem. effects of microwave irradn. on bimetallic electrocatalyst for glycerol oxidn. reaction, which open new opportunities for developing high-performance direct alk. glycerol fuel cells.
    67. 67
      Houache, M. S. E.; Shubair, A.; Sandoval, M. G.; Safari, R.; Botton, G. A.; Jasen, P. V.; González, E. A.; Baranova, E. A. Influence of Pd and Au on Electrochemical Valorization of Glycerol over Ni-Rich Surfaces. J. Catal. 2021, 396, 1– 13,  DOI: 10.1016/j.jcat.2021.02.008
      67
      Influence of Pd and Au on electrochemical valorization of glycerol over Ni-rich surfaces
      Houache, Mohamed S. E.; Shubair, Asma; Sandoval, Mario G.; Safari, Reza; Botton, Gianluigi A.; Jasen, Paula V.; Gonzalez, Estela A.; Baranova, Elena A.
      Journal of Catalysis (2021), 396 (), 1-13CODEN: JCTLA5; ISSN:0021-9517. (Elsevier Inc.)
      Herein the authors synthesized bi-metallic Pd@Ni and Au@Ni core-shell-like nanoparticles (NPs) for glycerol electrooxidn. reaction (GEOR) in alk. media. The morphol., structural and surface properties of the NPs were evaluated using a range of physicochem. techniques. The catalytic activity and stability were studied using the three-electrode electrochem. cell and 25 cm2- continuous electrolysis cell. Among different at. ratios, Ni80Pd20 and Ni90Au10 nanoparticles showed the highest current densities which are ∼4.5 and 4.2 times higher than spherical Ni, resp. The addn. of Pd and Au (<20 at.%) to Ni nanoparticles led to a remarkable glycerate selectivity of ∼73.1% and 65.7% for Ni80Pd20 and Ni90Au10 catalysts at 1.3 V and 50°, resp. Notably, after 6 h of electrolysis Pd@Ni and Au@Ni tend to suppress the C-C bond cleavage, compared to Ni at any applied potentials and temps. The DFT calcns. predicted that the addn. of Pd or Au to Ni reduces the work function of M@Ni NPs, which strengthens the OH adsorption and enhances the removal of GEOR intermediates.
    68. 68
      Wang, H.; Thia, L.; Li, N.; Ge, X.; Liu, Z.; Wang, X. Pd Nanoparticles on Carbon Nitride-Graphene for the Selective Electro-Oxidation of Glycerol in Alkaline Solution. ACS Catal. 2015, 5 (6), 3174– 3180,  DOI: 10.1021/acscatal.5b00183
      68
      Pd Nanoparticles on Carbon Nitride-Graphene for the Selective Electro-Oxidation of Glycerol in Alkaline Solution
      Wang, Haibo; Thia, Larissa; Li, Nan; Ge, Xiaoming; Liu, Zhaolin; Wang, Xin
      ACS Catalysis (2015), 5 (6), 3174-3180CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
      A hybrid support consisting of C nitride and graphene (CNx/G) was prepd. by annealing polypyrrole/GO at 800°. Pd nanoparticles (NPs) are then loaded onto the support by a microwave-polyol method. Pd-CNx/G was used as a catalyst for glycerol electrooxidn. in 0.5 M NaOH aq. soln. Electrochem. characterization and product anal. by HPLC show that, in comparison to Pd NPs supported on C black, Pd NPs on a support contg. N atoms has the ability to promote selectivity toward C3 products as well as increase activity. The main factors influencing the selectivity and activity are also discussed.
    69. 69
      Melle, G.; de Souza, M. B. C.; Santiago, P. V. B.; Corradini, P. G.; Mascaro, L. H.; Fernández, P. S.; Sitta, E. Glycerol Electro-Oxidation at Pt in Alkaline Media: Influence of Mass Transport and Cations. Electrochim. Acta 2021, 398, 139318,  DOI: 10.1016/j.electacta.2021.139318
      69
      Glycerol electro-oxidation at Pt in alkaline media: influence of mass transport and cations
      Melle, Gabriel; de Souza, Matheus B. C.; Santiago, Patricia V. B.; Corradini, Patricia Gon; Mascaro, Lucia Helena; Fernandez, Pablo S.; Sitta, Elton
      Electrochimica Acta (2021), 398 (), 139318CODEN: ELCAAV; ISSN:0013-4686. (Elsevier Ltd.)
      Glycerol is an important biomass-derived product with potential to be applied on energy converting systems or as platform mol. in electrosynthesis. In this work we studied the glycerol oxidn. reaction (GOR) in alk. media contg. distinct alk. cations and controlling the mass transport. The cyclic voltammograms were deconvoluted into three processes and the changes in the charge of each process revealed that mass transport affects the GOR in a complex matter, depending on both applied potential and electrolyte cation. Regardless of the cation on supporting electrolyte, high-performance liq. chromatog. (HPLC) anal. revealed the prodn. of glycerate and lactate during GOR. Finally, potential oscillations under current control were mapped, highlighting the influence of both cations and mass transport, even in the systems with very similar behavior under potential control.
    70. 70
      Zhou, Y.; Shen, Y.; Piao, J. Sustainable Conversion of Glycerol into Value-Added Chemicals by Selective Electro-Oxidation on Pt-Based Catalysts. ChemElectroChem 2018, 5 (13), 1636– 1643,  DOI: 10.1002/celc.201800309
      70
      Sustainable Conversion of Glycerol into Value-Added Chemicals by Selective Electro-Oxidation on Pt-Based Catalysts
      Zhou, Yongfang; Shen, Yi; Piao, Jinhua
      ChemElectroChem (2018), 5 (13), 1636-1643CODEN: CHEMRA; ISSN:2196-0216. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Electro-oxidn. of glycerol affords a totally green route to produce high value-added chems. Herein, we report a study on glycerol electro-oxidn. over a series of graphene nanosheet supported Pt (Pt/GNS), PtNi (PtNi/GNS), PtRu (PtRu/GNS), PtRh (PtRh/GNS), PtRuNi (PtRuNi/GNS), and PtRhNi (PtRhNi/GNS) catalysts in alk. soln. The activity of the catalysts was evaluated by cyclic voltammetry, linear sweep voltammetry, and chronoamperometric measurements. The PtRh/GNS and PtRhNi/GNS catalysts exhibited superior activity in terms of higher current densities and lower onset potentials. The products of glycerol oxidn. formed at potentials of -0.4, -0.1, and 0.2 V, were systematically analyzed by high performance liq. chromatog. (HPLC). Five compds. as products from glycerol electro-oxidn. catalyzed by the prepd. materials were found, including glyceraldehyde, glycolic acid, tartronic acid, glyceric acid and oxalate acid. The product distribution at the different potentials was investigated for all catalysts. A max. glycolic acid selectivity of 65.4 % was obtained for the Pt/GNS catalyst at 0.2 V while a max. glyceric acid selectivity of 47.7 % was achieved using the PtNi/GNS catalyst at -0.1 V. It was found that the introduction of Ru facilitated the formation of C3 products while the addn. of Rh was beneficial for the formation of C2 products. Based on HPLC results, the pathways of glycerol electro-oxidn. by the prepd. catalysts were proposed.
    71. 71
      Valter, M.; dos Santos, E. C.; Pettersson, L. G. M.; Hellman, A. Partial Electrooxidation of Glycerol on Close-Packed Transition Metal Surfaces: Insights from First-Principles Calculations. J. Phys. Chem. C 2020, 124 (33), 17907– 17915,  DOI: 10.1021/acs.jpcc.0c04002
      71
      Partial Electrooxidation of Glycerol on Close-Packed Transition Metal Surfaces: Insights from First-Principles Calculations
      Valter, Mikael; dos Santos, Egon Campos; Pettersson, Lars G. M.; Hellman, Anders
      Journal of Physical Chemistry C (2020), 124 (33), 17907-17915CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      Glycerol is a byproduct of biodiesel prodn. and an abundant feedstock for the synthesis of high-value chems. One promising approach for valorization of glycerol is electrooxidn. yielding H and value-added products. However, due to the vast amt. of intermediary steps and possible products, the process is not fully understood. Here, the 1st two deprotonations of glycerol on close-packed transition metals (Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, and Au) were studied using d. functional theory calcns. together with the computational H electrode. The theor. limiting potential for the studied reaction is ∼0 V vs. the reversible H electrode, ranging from -0.12 V for Ru to +0.35 V for Au. Also, Ru, Rh, Ir, Ag, and Au are selective toward dihydroxyacetone and its derivs., while Pd and Pt are selective toward either dihydroxyacetone or glyceraldehyde and their derivs., and that Cu, Co, and Ni are selective toward hydropyruvic acid. The results can be rationalized in terms of the relative bond strengths of C and O on the metal. Solvent effects are generally small, the exceptions being the limiting potential on Cu and the mechanism on Rh. These results can be used to steer the selectivity toward more valuable products and thereby increase the economic yield of biodiesel prodn.
    72. 72
      Valter, M.; Santos, E. C.; Pettersson, L. G. M.; Hellman, A. Selectivity of the First Two Glycerol Dehydrogenation Steps Determined Using Scaling Relationships. ACS Catal. 2021, 11 (6), 3487– 3497,  DOI: 10.1021/acscatal.0c04186
      72
      Selectivity of the First Two Glycerol Dehydrogenation Steps Determined Using Scaling Relationships
      Valter, Mikael; Santos, Egon Campos dos; Pettersson, Lars G. M.; Hellman, Anders
      ACS Catalysis (2021), 11 (6), 3487-3497CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
      Glycerol is a byproduct of biodiesel prodn. and an abundant feedstock that can be used for the synthesis of high-value chems. There are many approaches for glycerol valorization, but, due to the complicated reaction mechanism, controlling which products are produced is challenging. Here, we describe glycerol's chem. selectivity for different metallic catalysts using descriptors for carbon (mainly *C, *CH2OH) and oxygen (mainly *O, CH3O*). The quality of these descriptors and the weighted combinations thereof are validated based on their fit, via linear regression, to the binding energies of all reaction intermediates generated in the first two glycerol dehydrogenation steps on a no. of close-packed Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, and Au surfaces. We show that *CH2OH is a better descriptor than *C for the studied carbon-bound intermediates, which is attributed to the observation that the adjacent *OH group interacts with the surface. This leads to a neg. oxygen dependence, which can be generalized to similar alc.-derived adsorbates. Furthermore, we show that CH3O* is a better oxygen descriptor than *O for the studied intermediates. This is mainly attributed to the difference between the single and double bonds, as we show that *OH is closer to the accuracy of CH3O*. Multilinear regression with different combinations of *C, *O, and *OH is comparable in accuracy to that of *CH2OH and CH3O*. Scaling relationships are used to det. the selectivity map for glycerol dehydrogenation. The results show that the first dehydrogenation is selective toward two different intermediates (one bonded via the secondary carbon and the other via the secondary oxygen) depending on the relative bond strength of the carbon and oxygen descriptors. The second dehydrogenation step results in five intermediates, again depending primarily on the relative bond strength of carbon and oxygen to the surface. The selectivity maps can be used together with kinetic considerations and exptl. data to find catalyst candidates for glycerol dehydrogenation.
    73. 73
      Yu, X.; dos Santos, E. C.; White, J.; Salazar-Alvarez, G.; Pettersson, L. G. M.; Cornell, A.; Johnsson, M. Electrocatalytic Glycerol Oxidation with Concurrent Hydrogen Evolution Utilizing an Efficient MoOx/Pt Catalyst. Small 2021, 17 (44), 2104288,  DOI: 10.1002/smll.202104288
      73
      Electrocatalytic Glycerol Oxidation with Concurrent Hydrogen Evolution Utilizing an Efficient MoOx/Pt Catalyst
      Yu, Xiaowen; dos Santos, Egon Campos; White, Jai; Salazar-Alvarez, German; Pettersson, Lars G. M.; Cornell, Ann; Johnsson, Mats
      Small (2021), 17 (44), 2104288CODEN: SMALBC; ISSN:1613-6810. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Glycerol electrolysis affords a green and energetically favorable route for the prodn. of value-added chems. at the anode and H2 prodn. in parallel at the cathode. Here, a facile method for trapping Pt nanoparticles at oxygen vacancies of molybdenum oxide (MoOx) nanosheets, yielding a high-performance MoOx/Pt composite electrocatalyst for both the glycerol oxidn. reaction (GOR) and the hydrogen evolution reaction (HER) in alk. electrolytes, is reported. Combined electrochem. expts. and theor. calcns. reveal the important role of MoOx nanosheets for the adsorption of glycerol mols. in GOR and the dissocn. of water mols. in HER, as well as the strong electronic interaction with Pt. The MoOx/Pt composite thus significantly enhances the specific mass activity of Pt and the kinetics for both reactions. With MoOx/Pt electrodes serving as both cathode and anode, two-electrode glycerol electrolysis is achieved at a cell voltage of 0.70 V to reach a c.d. of 10 mA cm-2, which is 0.90 V less than that required for water electrolysis.
    74. 74
      Yaylayan, V.; Harty-Majors, S.; Ismail, A. Investigation of Dl-Glyceraldehyde-Dihydroxyacetone Interconversion by FTIR Spectroscopy. Carbohydr. Res. 1999, 318 (1–4), 20– 25,  DOI: 10.1016/S0008-6215(99)00077-4
      74
      Investigation of DL-glyceraldehyde-dihydroxyacetone interconversion by FTIR spectroscopy
      Yaylayan, V. A.; Harty-Majors, S.; Ismail, A. A.
      Carbohydrate Research (1999), 318 (1-4), 20-25CODEN: CRBRAT; ISSN:0008-6215. (Elsevier Science Ltd.)
      Interconversion of dihydroxyacetone and DL-glyceraldehyde was studied in different solvents and temps. by FTIR spectroscopy. Dissoln. in water or triethylamine, and increasing temps. caused the dissocn. of the dimeric forms of both compds. into monomers and subsequently inter-conversion of dihydroxyacetone and DL-glyceraldehyde. Dioxane, on the other hand, did not initiate such inter-conversions. FTIR anal. in different solvents has also indicated that monomeric DL-glyceraldehyde can exist in two distinct intramolecularly H-bonded forms. A five-membered ring form was predominant in aq. solns. of the dissocd. DL-glyceraldehyde dimer, whereas a six-membered ring form was preferred in triethylamine soln. or in aq. soln. of dissocd. dihydroxyacetone dimer. However, in aq. solns. of DL-glyceraldehyde dimer, the five-membered ring conformation was slowly transformed into the six-membered ring form under slightly basic pH. In addn., dihydroxyacetone predominantly converted into the six-membered H-bonded conformation of glyceraldehyde when dissolved in water. This was attributed to the preferential formation of the trans- or E-enediol as an intermediate. Temp.-dependent spectra have also indicated that increasing the temp. favored the formation of glyceraldehyde in the aq. equil. mixts. of dimeric DL-glyceraldehyde and dihydroxyacetone.
    75. 75
      Rasrendra, C. B.; Fachri, B. A.; Makertihartha, I. G. B. N.; Adisasmito, S.; Heeres, H. J. Catalytic Conversion of Dihydroxyacetone to Lactic Acid Using Metal Salts in Water. ChemSusChem 2011, 4 (6), 768– 777,  DOI: 10.1002/cssc.201000457
      75
      Catalytic Conversion of Dihydroxyacetone to Lactic Acid Using Metal Salts in Water
      Rasrendra, Carolus B.; Fachri, Boy A.; Makertihartha, I. Gusti B. N.; Adisasmito, Sanggono; Heeres, Hero J.
      ChemSusChem (2011), 4 (6), 768-777CODEN: CHEMIZ; ISSN:1864-5631. (Wiley-VCH Verlag GmbH & Co. KGaA)
      We herein present a study on the application of homogeneous catalysts in the form of metal salts on the conversion of trioses, such as dihydroxyacetone (DHA), and glyceraldehyde (GLY) to lactic acid (LA) in water. A wide range of metal salts (26 in total) were examd. AlIII salts were identified as the most promising and essentially quant. LA yields (>90 mol %) were obtained at 140 °C and a reaction time of 90 min. A reaction pathway is proposed and a kinetic model using the power law approach was developed for the conversion of DHA to LA with pyruvaldehyde (PRV) as the intermediate. Good agreement between exptl. data and the model was obtained. Model predictions, supported by expts., indicate that a high yield of LA is favored in dil. solns. of DHA (0.1 M) at elevated temps. (180 °C) and reaction times less than 10 min.
    76. 76
      Denis, W. On the Behaviour of Various Aldehydes, Ketones and Alcohols towards Oxidizing Agents. Am. Chem. J. 1907, 38, 561– 594
      There is no corresponding record for this reference.
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      Fedoroňko, M.; Königstein, J. Kinetics of Mutual Isomerization of Trioses and Their Dehydration to Methylglyoxal. Collect. Czech. Chem. Commun. 1969, 34, 3881– 3894,  DOI: 10.1135/cccc19693881
      77
      Kinetics of mutual isomerization of trioses and their dehydration to methyl glyoxal
      Fedoronko, Michal; Koenigstein, Jozef
      Collection of Czechoslovak Chemical Communications (1969), 34 (12), 3881-94CODEN: CCCCAK; ISSN:0010-0765.
      The acid-base catalyzed transformations of DL-glyceraldehyde (I) and dihydroxyacetone (II) and their irreversible dehydration to methyl glyoxal (III) were studied in aq. HCl and NaOH solns., and in phosphate an d carbonate buffers to fine the kinetics of the mutual isomerization of trioses; concns. were detd. polarog. In aq. HCl solns. only dehydration of I or II to III was obsd.; no mutual isomerization occurred. In acetate, phosphate, and carbonate buffers as well as in NaOH solns., however, not only dehydration, but also mutual isomerization proceeds. Rate consts. of these reactions, as well as catalytic rate consts., were detd. The values of activation energies were detd. using the Arrhenius equation. The dehydrations of trioses studied are acid-base catalyzed reactions, while their mutual isomerization is general base catalyzed; the rate consts. of isomerization are several times higher than those of the corresponding dehydrations.

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