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The Effect of the Pd Precursors on the Shape of Hollow Ag–Pd Alloy Nanoparticles Using Ag Nanocubes as Seeds
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The Effect of the Pd Precursors on the Shape of Hollow Ag–Pd Alloy Nanoparticles Using Ag Nanocubes as Seeds
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  • Xin Wen
    Xin Wen
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-412-96 Gothenburg, Sweden
    More by Xin Wen
  • Seyed Amirabbas Nazemi
    Seyed Amirabbas Nazemi
    Department of Physics, Engineering, Earth, Environmental sciences, and Mechanics, University of Grenoble Alpes, 38400 Saint Martin d’Hères, France
    School of Life Science, University of Applied Sciences and Arts Northwestern Switzerlanz, Hofackerstrasee 30, Muttenz CH-4132, Switzerland
    More by Seyed Amirabbas Nazemi
  • Robson Rosa da Silva*
    Robson Rosa da Silva
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-412-96 Gothenburg, Sweden
    NanoScientifica Scandinavia AB, Stena Center, Studio 4166, 41 292 Gothenburg, Sweden
    *Email: [email protected]
    More by Robson Rosa da Silva
  • Kasper Moth-Poulsen*
    Kasper Moth-Poulsen
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-412-96 Gothenburg, Sweden
    The Institute of Materials Science of Barcelona, ICMAB-CSIC, Bellaterra, 08193 Barcelona, Spain
    Catalan Institution for Research & Advanced Studies, ICREA, Pg. Llu′ıs Companys 23, 08010 Barcelona, Spain
    Department of Chemical Engineering, Universitat Politècnica de Catalunya, EEBE, Eduard Maristany 10−14, 08019 Barcelona, Spain
    *Email: [email protected]
    More by Kasper Moth-Poulsen
    Orcidhttps://orcid.org/0000-0003-4018-4927
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Langmuir

Cite this: Langmuir 2023, 39, 32, 11268–11273
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https://doi.org/10.1021/acs.langmuir.3c00799
Published July 28, 2023

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Abstract

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Hollow Ag–Pd nanoparticles have potentially high catalytic performance owing to their larger surface area compared to their corresponding solid nanoparticles. We successfully fabricated hollow Ag–Pd alloy nanodendrites and nanoboxes by using different Pd precursors (H2PdCl4 and Pd(acac)2) to achieve large surface area nanoboxes. Interestingly, the use of a H2PdCl4 precursor led to the formation of hollow nanodendrite structures, whereas the slower reduction of Pd(acac)2 led to the formation of hollow nanoboxes. The microstructure and chemical composition of Ag–Pd nanoparticles and properties of their growth solutions were investigated by transmission electron microscopy, energy-dispersive X-ray spectroscopy, and ultraviolet–visible spectroscopy.

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Introduction

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Hollow nanostructures have been studied in different metallic materials. As compared to their solid counterparts, hollow nanoparticles have lower weight and higher surface area, which potentially improves the mass efficiency of noble metallic materials and their properties. (1−3) Catalytic activity is one of the most important properties of metallic nanoparticles. (4,5) The interior empty space of hollow nanoparticles enlarges the active surface area, making the nanoparticles highly accessible for reactants. (6,7) Particularly, the interior catalytic sites are not impressionable to aggregation of the nanoparticles, which could enhance the catalytic activity further. (3) Additionally, in hollow catalysts, the reactants often access the inner surface via diffusion through the shell of hollow nanoparticles. The diffusion rate depends on the porosity and thickness of the hollow shell and properties of reactants. Therefore, controlling the hollow structure can improve selectivity of catalytic reactions. (8) Surface plasmon resonance, another important property of noble metallic nanoparticles, can be influenced by the existence of hollow structures in the nanoparticles, which is of high importance for their applications in photonic devices and drug delivery. (2,9)
Studies on hollow palladium (Pd) nanoparticles attract considerable attention as Pd is one of the most valuable metals and its nanoparticles have high catalytic abilities on carbon–carbon coupling and hydrogenation reactions. (10,11) Carbon–carbon coupling reactions are often used in the synthesis of pharmaceutical compounds in industry, which has led to an increased utilization of Pd as a catalyst in last 20 years. (12) The high hydrogen-adsorption ability of Pd makes it an excellent candidate as a sensing material for hydrogen gas sensor and hydrogen storage. (13,14) Nowadays, new catalytic technologies prioritize green catalysts, preventing from human impact at the beginning, rather than environmental remediation after contamination. The catalytic properties could be improved by tailoring the electronic structure of catalytic materials through modification of their microstructure and composition. (15) Therefore, the synthesis process and structure of materials are important for realization of green catalysts.
One of the most common synthesis methods for hollow Ag–Pd nanoparticles is the double-template method where a sacrificial nanomaterial is overgrown with Pd and oxidized in the process, through galvanic replacement. This method is advantageous in a number of aspects: (a) the synthesis process is simple, versatile, and environmentally friendly; (b) reaction conditions are mild; (c) the size and shape of Ag–Pd nanoparticles are easily controlled; and (d) the synthesis process is highly reproducible. (16,17) By this approach, a type of metal nanoparticle is used as the hard template and sacrificed through a galvanic replacement reaction with Pd ions from different Pd precursors. (18) It requires the template metal to have a lower redox potential in order to undergo spontaneous redox reaction between surficial metal template atoms and Pd ions. (19) For instance, the template could be nickel (Ni) for hollow Pd–Ni alloy nanoparticles, (2,20) copper(I) oxide (Cu2O) for Ag–Pd nanospheres, (21) and silver (Ag) for Ag–Pd alloy nanoparticles. As Ag is comparatively cheap and easy to get oxidized under reaction conditions, it was selected as a sacrificial template in our experiments. In the double-template method, surfactants or polymers can be used as a soft template to stabilize the shape and size of hollow metallic nanoparticles. (18) Therefore, the shape can be influenced by using different surfactants. For example, hexadecyltrimethylammonium bromide (CTAB) is often used to synthesize Ag–Pd nanocubes, while Ag–Pd nanodendrites can be obtained by using a mixture of hexadecyltrimethylammonium chloride (CTAC) and sodium oleate (NaOL). (22,23) Additionally, parameters such as pH value, reaction temperature, and concentrations of reagents can affect the shape and size of Ag–Pd nanoparticles. (24)
Even though some studies have been done on the synthesis and catalytic properties of hollow Ag–Pd nanoparticles, there are no comprehensive studies on the effects of Pd precursors on the formation of hollow Ag–Pd nanoparticles. (25−27) Since different Pd salts perform a variety of physical and chemical properties, the selection of Pd precursors may influence the synthesis process and the final shape of nanoparticles. Additionally, the catalytic properties vary with crystal facets of hollow Ag–Pd nanoparticles and the facets with high catalytic activity are expected to be formed. (28) Therefore, it is necessary to study the effects of Pd precursors in shape, physical, and catalytic properties of the hollow Ag–Pd nanoparticles.
In this work, we used dihydrogen tetrachloropalladate (H2PdCl4) and palladium(II) acetylacetonate (Pd(acac)2) as precursors and Ag nanocubes as a hard template to synthesize hollow Ag–Pd nanoparticles with different shapes. The microstructure and chemical composition of these hollow Ag–Pd nanoparticles have been investigated by transmission electron microscopy.

Experimental Section

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Materials

Palladium(II) chloride (PdCl2, 99%), palladium(II) acetylacetonate (Pd(acac)2, 99%), silver trifluoroacetate (CF3COOAg, 98%), polyvinylpyrrolidone (PVP, Mw = 55,000), l-ascorbic acid (AA, 99%), sodium hydrosulfide hydrate (NaHS·xH2O), and hydrochloric acid (HCl, 37 wt % in water) were purchased from Sigma-Aldrich. NaOL (>97.0%) was obtained from Tokyo Chemical Industry. CTAC (99%) was purchased from Acros Organics of Fisher Scientific. Acetone (≥99.8%) and methanol (≥99.9%) were obtained from Fisher Scientific. Ethylene glycol (EG, ≥99%) was purchased from J.T.Baker Chemical (Avantor Performance Materials, LLC).
The Milli-Q water used in the solutions is ultrapure water 18.2MΩ.cm purified with a Milli-Q Advantage A10 water purification system from Merck. 10 mM of H2PdCl4 solution was prepared by dissolving 88.65 mg of PdCl2 in 50 mL of 20 mM HCl in a water bath at 60 °C. As Pd(acac)2 is insoluble in water, 10 mM of Pd(acac)2 solution was freshly prepared by adding 15.23 mg of Pd(acac)2 in 5 mL of Milli-Q water and mixing for several seconds on a vortex followed by the addition of 10 mL of methanol. The mixture was mixed thoroughly on the vortex for 5 min and added in the reaction directly to prevent Pd ions from reduction of methanol. Additionally, CTAC and NaOL aqueous solutions were stored in a water bath at 40 °C until use.

Synthesis of Ag Nanocubes

The synthesis of the Ag nanocubes was initially adapted from the method described by Zhang et al. (29) and Wand et al. (30) All reagents were prepared in EG solvent.
Briefly, 50 mL of EG was added into a 250 mL round-bottom flask and incubated in an oil bath at 150 °C for 1 h, while the solution was stirred at a speed of 550 rpm. Then, 0.6 mL of 3 mM NaHS was injected in the heated solution. After 4 min, 5 mL of 3 mM HCl solution was added. 2 min later, 12.5 mL of PVP solution (20 mg/mL) was added in the flask. After another 2 min, 4 mL of 282 mM CF3COOAg was injected. The reaction solution was incubated at 150 °C for 30 min, while stirring continuously. During the entire process, the outlet of the flask was sealed except for the time of reagent addition. Finally, the round-bottom flask containing the prepared Ag nanocubes was placed into an ice bath to quench the reaction and stop the further growth of Ag nanocubes.
For purification, 7.5 mL of prepared Ag nanocube suspension was mixed with 42.5 mL of acetone in a 50 mL centrifuge tube and then centrifuged at 4900 rpm (2797 RCF) for 8 min. After removing the supernatant, Ag nanocubes were dispersed in 1.5 mL of Milli-Q water using the vortex and ultrasonication and then transferred into a 1.5 mL Eppendorf centrifuge tube. The Ag nanocube suspension was centrifuged (VWR Micro Star 12) again at 13,500 rpm (12,300 RCF) for 15 min. 1 mL of Milli-Q water was added after the supernatant was removed. This Ag nanocube suspension was stored at room temperature for future use.

Synthesis of Hollow Ag–Pd Nanodendrites

The growth of Ag–Pd nanodendrites on Ag nanocubes was adapted and modified based on our previously reported method. (23) An optimal molar ratio of CTAC and NaOL (4:1) was applied in our synthesis. 4 mL of 50 mM CTAC and 1 mL of 50 mM NaOL aqueous solutions were mixed well in a 20 mL glass vial. After that, 25 μL of Ag nanocube suspension was added as seeds. Finally, 25 μL of 100 mM AA and 125 μL of 10 mM H2PdCl4 solutions were added in sequence. This solution mixture was mixed thoroughly on the vortex and then transferred to a water bath at 40 °C for 4 h without stirring. The final product was centrifuged at 12,000 rpm (9700 RCF) for 10 min. After removing the supernatant, the hollow Ag–Pd nanodendrites were dispersed in the same volume of Milli-Q water.

Synthesis of Hollow Ag–Pd Spiky Nanoboxes

The synthesis of hollow Ag–Pd spiky nanoboxes was followed by the same procedure of the synthesis of hollow Ag–Pd nanodendrites, but this time, 375 μL of Pd(acac)2 in the mixture of water and methanol was used as a Pd source, which contained the same amount of Pd ions as H2PdCl4 in the growth solution of hollow Ag–Pd nanodendrites. Since the Ag–Pd nanoboxes grew more slowly than the Ag–Pd nanodendrites (Figure S1 of the ESI for more details), the mixed growth solution for hollow Ag–Pd nanoboxes was incubated in a water bath at 40 °C for longer hours (22 h).

Characterization

UV–visible extinction spectra were taken on an Agilent Cary 100 UV–vis spectrophotometer at room temperature. The zeta potential of nanoparticle suspensions was investigated on a Malvern Panalytical Zetasizer Nano ZS. The microstructure of nanoparticles was studied with a FEI Tecnai T20 transmission electron microscope (TEM) at 200 kV, FEI Titan 80–300 TEM at 300 kV, and a JEOL JEM-1200EX II TEM at 120 kV.

Results and Discussion

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In our experiments, H2PdCl4 and Pd(acac)2 were used as Pd precursors, respectively, in the seed-mediated growth of hollow Ag–Pd nanoparticles, where the Ag seeds were sacrificed by a galvanic replacement reaction with the Pd precursors. The schematic illustration of this process is displayed in Figure 1. A certain amount of Ag nanocubes was added as the seeds in the growth solution containing one type of Pd precursors, CTAC and NaOL as capping agents, and AA as a reducing agent. Where H2PdCl4 was employed, cubic Ag–Pd nanodendrites were formed after a 4 h growth. An empty cubic core with similar size and shape with the Ag seed can be observed by contrast in the corresponding TEM images (Figure 2). However, where Pd(acac)2 was used as the precursor, hollow Ag–Pd nanoboxes were formed. The empty cubic core can be clearly detected by contrast in TEM images (Figure 2). Moreover, four corners of these nanoboxes grew further forming spiky tips.

Figure 1

Figure 1. Schematic illustration of the synthesis process of hollow Ag–Ag–Pd nanodendrites and Ag–Ag–Pd nanoboxes. TEM images of Ag nanocubes, hollow Ag–Pd nanodendrites, and hollow Ag–Pd nanoboxes are inserted next to their models.

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Figure 2

Figure 2. Low-magnification TEM images (LM), high-magnification images (HM), and selected area electron diffraction patterns (SAED) are shown in sequence. (a) LM, (b) HM, and (c) SAED for Ag nanocubes. (d) LM, (e) HM, and (f) SAED for Ag–Pd nanodendrites. (g) LM, (h) HM, and (i) SAED for Ag–Pd nanoboxes. The average size of each nanoparticle is marked in the corresponding low-magnification TEM image. Histograms of the size distribution are shown in Figure S2 of ESI. (j) Energy-dispersive X-ray spectroscopy (EDS) spectrum of Ag–Pd nanodendrites. (k) EDS spectrum of Ag–Pd nanoboxes.

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The quality of these Ag nanocubes, hollow Ag–Pd nanodendrites, and nanoboxes was investigated by TEM imaging at different magnifications and selected area electron diffraction (SAED) patterns, shown in Figure 2. The TEM images of Ag nanocubes in Figure 2a,b indicate that a high yield of cubic Ag seeds with an average size of 30.2 ± 6.2 nm has been produced. The diffraction rings from inner to outer ones in the SAED pattern of these Ag nanocubes correspond to (111), (200), (220), and (311) lattice planes of Ag crystals (marked in Figure 2c), respectively, verifying that these Ag nanocubes consist of Ag crystals.
TEM images of hollow Ag–Pd nanodendrites presented in Figure 2d,e suggest a high yield and uniform shape with a measured average size of 54.3 ± 7.1 nm. The TEM images of hollow Ag–Pd nanoboxes (Figure 2g,h) also verify them to have a high yield and uniform shape. The average size of the Ag–Pd nanoboxes is measured to be 45.4 ± 5.9 nm, slightly smaller than the Ag–Pd nanodendrites. SAED patterns of hollow Ag–Pd nanodendrites and nanoboxes were produced to identify their crystal structures, as shown in Figure 2f,i. SAED patterns of both nanoparticles present classical polycrystal diffraction characteristics of face-centered cubic (FCC) structure. However, the interplanar crystal spacings of (111), (200), (220), and (311) lattice planes measured from the SAED patterns are slightly larger than the values of Pd crystals, which raises our suspicion on the chemical composition of these hollow Ag–Pd nanodendrites and nanoboxes. Therefore, energy-dispersive X-ray spectroscopy (EDS) was performed on these two hollow nanostructures and the results are shown in Figure 2j,k. Strong peaks of Ag and Pd elements are discovered in both EDS spectra, except for the peaks of Cu and C from the TEM grids and the elements from reaction reagents such as Cl and S. This indicates that a portion of Ag remains in the lattice of hollow Pd structures. Additionally, an average atomic percent of Ag in the Ag–Pd nanostructure was calculated by performing EDS on three more regions (shown in Table S1 of the ESI). The results verify that hollow Ag–Pd nanodendrites consist of 43% of Pd and 57% of Ag and hollow Ag–Pd nanoboxes contain 41% of Pd and 59% of Ag.
Even though the EDS spectra in Figure 2 confirm that these hollow Ag–Pd nanoparticles contain a high percent of Ag, it is still unclear if Ag and Pd elements form a core–shell structure or alloy. Therefore, further EDS mapping was performed to investigate the distribution of Ag and Pd and the results are depicted in Figure 3. The mappings of Ag and Pd in Figure 3a indicate that both elements distribute over the entire nanodendrites. The signals of Ag and Pd are mixed evenly, and no core–shell structure can be observed from the mapping of Ag–Pd overlay. However, comparing the signal intensity, signified by the color intensity, between the edge and center regions, both Ag and Pd have stronger signals at the edge than the center of the nanodendrites, indicating the existence of the empty cores, which is consistent with the observation on TEM and STEM images. The same result is obtained from the EDS mapping of hollow Ag–Pd nanoboxes in Figure 3b. Ag and Pd elements are mixed evenly and distributed over the whole nanoboxes. The empty cores in the center of the particles can be observed by the signal intensity difference in the mappings of Ag, Pd, and Ag–Pd overlay. Therefore, the results in Figure 3 verify that the nanoparticles synthesized in this work are hollow Ag–Pd alloys.

Figure 3

Figure 3. EDS mapping of hollow Ag–Pd nanoparticles, including a scanning transmission electron microscope (STEM) image of the particles and mappings of Ag, Pd, and Ag–Pd overlay. (a) Nanodendrites, where green is Ag and yellow is Pd. (b) Nanoboxes, where red is Ag and purple is Pd.

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In order to further verify the crystalline structure of the nanoparticles, X-ray powder diffraction (XRD) was conducted for both nanoboxes and nanodendrites. The results are presented in Figure 4.

Figure 4

Figure 4. X-ray diffraction pattern of Ag-Pd the Ag−Pd nanoboxes and nanodendrites (a) and, a zoomed view of the spectra in the region 37°−48° (b). Reference peaks are shown in green and blue lines.

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The XRD measurement reveals a homogenous alloy structure of the Ag–Pd nanodendrites with a 50/50 fraction of each, while the spectrum of the nanoboxes indicates that there is a two-fold Ag-rich fraction compared to Pd. As can be seen, there are few peaks present in the measurements, which can be explained by the unreacted chemicals and/or unbound ligands within the samples. This set of results along with EDS measurements verifies the crystalline structure of the Ag–Pd nanoboxes and nanodendrite alloys.
High-resolution TEM was carried out at different magnifications to investigate the microstructure of hollow Ag–Pd nanodendrites and nanoboxes in detail. Figure 5a displays a high-resolution TEM image of a single Ag–Pd nanobox. The Fast Fourier transform (FFT) image presented in Figure 5b shows a polycrystal characteristic, but the spots of (200) and (111) lattice planes are clear and have strong intensities, illustrating that the Ag–Pd nanobox consists of several crystals. (200) lattice planes are marked by a pair of parallel red lines in Figure 4a. The interplanar crystal spacings of (111), 0.23 nm, and (200), 0.19 nm, were also measured from the FFT. Based on these values and the fundamental rules of FCC, the lattice constant of the crystal structure of hollow Ag–Pd nanoboxes is deduced to be 0.40 nm, which is between the values of the Pd crystal (0.39 nm and Ag crystal (0.41 nm).

Figure 5

Figure 5. (a) High-resolution TEM image of an entire hollow Ag–Pd nanobox. The (200) lattice plane is noted by a pair of parallel red lines, and its interplanar spacing is recorded in the image. (b) The corresponding FFT of (a). Interplanar spacings of (111) and (200) lattice planes are marked in the image. (c) The FFT of (d). (d) High-resolution TEM image of the spiky corner, marked by a red square in (a). The (111) lattice plane and its interplanar spacing are recorded. (e) High-resolution TEM image of an entire hollow Ag–Pd nanodendrite. (f) The corresponding FFT of (e). The interplanar spacings of (111) and (200) lattice planes are recorded in the image. (g) The FFT of (h). (h) High-resolution TEM image of the dendrite marked by a red square in (e). The (111) lattice plane is marked by a pair of parallel red lines, and its interplanar spacing is recorded in the image.

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In order to clarify the growth of spiky corners in the nanoboxes, a magnified high-resolution TEM image of the corner marked by a red square in Figure 5a and its FFT are shown in Figure 5c and d, respectively. The (111) lattice planes, marked by a pair of parallel red lines in Figure 5d, can clearly be observed, which illustrates that the spiky corner grew along the (111) lattice planes, the close-packed planes of the FCC structure. The growth along close-packed planes can achieve a stable structure with the lowest surface energy. (31,32) This result also explains why there are (111) spots with strong intensities in Figure 5b.
A similar analysis was performed on the hollow Ag–Pd nanodendrites. Figure 5e and f display a high-resolution TEM image of a single nanodendrite and its corresponding FFT, respectively. Compared to the nanobox, the FFT in Figure 5f presents a more typical characteristic of polycrystals, forming clear rings. It illustrates that the Ag–Pd nanodendrite consists of a large number of small dendrites, which can be observed easily from the high-resolution TEM image as well. Moreover, the interplanar spacings of (111) and (200) lattices were calculated from the FFT image as well, where d(111) = 0.2333 nm and d(200) = 0.2027 nm. Furthermore, the lattice constant of the FCC structure of hollow Ag–Pd nanodendrites is deduced to be 0.4047 nm, which is in between the lattice constants of Pd and Ag crystals as well.
A magnified TEM image of a tiny dendrite from the region marked by a red square in Figure 5e is presented in Figure 5h to study its growth. Both the TEM image and its corresponding FFT in Figure 5g and h, respectively, verify that the small dendrite also grew along the close-packed planes of the FCC structure and (111) lattice planes.
The reason why different shapes of hollow Ag–Pd alloy nanoparticles are formed by using H2PdCl4 and Pd(acac)2 as precursors, respectively, may be explained by their solubility in water. Based on the previously proposed model, (23) the surfactant mixture of CTAC and NaOL forms mixed micelles through their opposite charges on the surface of the Ag seeds. PdCl42– ions interact with positively charged cetyltrimethylammonium cation (CTA+) but repulsed by the negatively charged NaOL molecules. (33) Based on the model, the Pd precursor is attracted by the positively charged CTAB molecules in the mixed micelles located on the solid surface region and reduced there, leading to the formation of small dendrites.
However, Pd(acac)2 is insoluble in water. This is why methanol was introduced to assist in its dissolution. Pd(acac)2 has a much weaker interaction with the charges of the surfactants due to its poor solubility in aqueous solution. Additionally, the limited solubility of Pd(acac)2 also restricts the reduction rate of Pd(II) ions, which extends the growth period of the Ag–Pd nanoboxes.
Additionally, the effect of the seed content on the growth of hollow Ag–Pd nanodendrites was investigated and the results are shown in Figure S3 of the ESI. It illustrates that the size of the nanodendrites decreases as the content of Ag nanocubes seed suspension increases, but the shape of the nanodendrites does not experience noticeable change. Besides H2PdCl4 and Pd(acac)2, palladium(II) acetate (Pd(acetate)2) and sodium tetrachloropalladate (Na2PdCl4) were also used as Pd precursors to grow hollow Ag–Pd nanoparticles. The TEM images in Figure S5 of the ESI verify that these two Pd precursors result in the growth of nanodendrites as well. This result infers that the solubility of palladium salt precursors is a crucial parameter in achieving different Ag–Pd particle morphologies. Finally, in order to gain insights into the effect of CTAC in the growth of Ag–Pd nanostructures, we replaced CTAC with potassium halide salts (i.e., KF, KCl, KBr, and KI) under the same stochiometric ratio while H2PdCl4 was used as a precursor. In the presence of a mixture of NaOL and halide ions, substantial shape degradation of the nanocube seed morphology was observed with concomitant formation of small nanoparticles, as shown in Figure S6 of the ESI. This result is supported by our previous efforts identifying the shortcomings of the colloidal stability of nanoparticles in the presence of CTAC/NaOL binary solution, which revealed that the stoichiometry of cationic and anionic surfactants is crucial for nanoparticle morphology control. (23,34)

Conclusions

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In this work, hollow Ag–Pd alloy nanodendrites and nanoboxes were synthesized successfully by using H2PdCl4 and Pd(acac)2, respectively, as precursors. It illustrates that the type of precursors influences the shape of final nanoparticles. These hollow Ag–Pd nanoparticles were further studied by TEM techniques. The experimental results confirm that the Ag element remains in the Pd lattice of the hollow Ag–Pd nanoparticles during the growth process, forming alloys. There is 57% of Ag in the nanodendrites and 59% of Ag in the nanoboxes by atomic percent. These Ag–Pd alloys still form FCC lattice structures with the lattice constants between the constants of Ag and Pd crystals, which is 0.4047 nm for the nanodendrite and 0.3991 nm for the nanobox. Additionally, the high-resolution TEM results verify that the small dendrites of the nanodendrites and the spiky corners of the nanoboxes both grew along the close-packed (111) lattice planes to achieve a stable structure with the lowest surface energy.

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.langmuir.3c00799.

  • TEM images of hollow Ag–Pd nanodendrites and nanoboxes at different growth times; histograms of the size distribution of Ag nanocubes, hollow Ag–Pd nanodendrites, and nanoboxes; atomic percent of Ag and Pd in hollow Ag–Pd nanodendrites and nanoboxes detected by energy-dispersive X-ray spectroscopy from four regions and their average percent; extinction spectra and TEM images of hollow Ag–Pd nanodendrites synthesized by adding 5, 25, and 100 μL of Ag seed suspension, respectively; histograms of the size distribution of the hollow Ag–Pd nanodendrites; TEM images of hollow Ag–Pd nanodendrites synthesized by using palladium(II) acetate and sodium tetrachloropalladate as Pd precursors; TEM images of Ag–Pd particles prepared using the standard procedure except that no CTAC was replaced by the same molar concentration of KF, KCl, KBr, and KI (PDF)

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Author Information

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  • Corresponding Authors
    • Robson Rosa da Silva - Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-412-96 Gothenburg, Sweden;  NanoScientifica Scandinavia AB, Stena Center, Studio 4166, 41 292 Gothenburg, Sweden;  Email: [email protected]
    • Kasper Moth-Poulsen - Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-412-96 Gothenburg, Sweden;  The Institute of Materials Science of Barcelona, ICMAB-CSIC, Bellaterra, 08193 Barcelona, Spain;  Catalan Institution for Research & Advanced Studies, ICREA, Pg. Llu′ıs Companys 23, 08010 Barcelona, Spain;  Department of Chemical Engineering, Universitat Politècnica de Catalunya, EEBE, Eduard Maristany 10−14, 08019 Barcelona, Spain;  Orcidhttps://orcid.org/0000-0003-4018-4927;  Email: [email protected]
  • Authors
    • Xin Wen - Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-412-96 Gothenburg, Sweden;  Present Address: Smoltek Hydrogen AB, Otterhällegatan 1, SE-411 18 Gothenburg, Sweden (X.W.)
    • Seyed Amirabbas Nazemi - Department of Physics, Engineering, Earth, Environmental sciences, and Mechanics, University of Grenoble Alpes, 38400 Saint Martin d’Hères, France;  School of Life Science, University of Applied Sciences and Arts Northwestern Switzerlanz, Hofackerstrasee 30, Muttenz CH-4132, Switzerland
  • Author Contributions

    The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. X.W. and S.A.N. contributed equally.

  • Funding

    This work is supported from the Knut and Alice Wallenberg Foundation and the Swedish Research Council.

  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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We acknowledge financial support from the Knut and Alice Wallenberg Foundation and the Swedish Research Council.

References

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This article references 34 other publications.

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    Liang, H.-P.; Wan, L.-J.; Bai, C.-L.; Jiang, L. Gold Hollow Nanospheres: Tunable Surface Plasmon Resonance Controlled by Interior-Cavity Sizes. J. Phys. Chem. B 2005, 109, 7795– 7800,  DOI: 10.1021/jp045006f
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    Gold Hollow Nanospheres: Tunable Surface Plasmon Resonance Controlled by Interior-Cavity Sizes
    Liang, Han-Pu; Wan, Li-Jun; Bai, Chun-Li; Jiang, Li
    Journal of Physical Chemistry B (2005), 109 (16), 7795-7800CODEN: JPCBFK; ISSN:1520-6106. (American Chemical Society)
    Uniform gold hollow nanospheres with tunable interior-cavity sizes were fabricated by using Co nanoparticles as sacrificial templates and varying the stoichiometric ratio of starting material HAuCl4 over the reductants. The formation of these hollow nanostructures is attributed to two subsequent redn. reactions: the initial redn. of HAuCl4 by Co nanoparticles, followed by the redn. by NaBH4. In addn., a thick layer of silica was successfully coated onto the gold hollow nanospheres. These nanostructures are extensively characterized by TEM, XRD, HRTEM, SEM, electron diffraction, energy-dispersive X-ray anal., and UV-visible absorption spectroscopy. It is evident that the SPR peak locations corresponding to these hollow nanospheres are shifted over a region of more than 100 nm wavelength due to changes of shell thickness, which make these optically active nanostructures of great interest in both fundamental research and practical applications.
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    Wang, L.; Yamauchi, Y. Metallic Nanocages: Synthesis of Bimetallic Pt–Pd Hollow Nanoparticles with Dendritic Shells by Selective Chemical Etching. J. Am. Chem. Soc. 2013, 135, 16762– 16765,  DOI: 10.1021/ja407773x
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    Metallic Nanocages: Synthesis of Bimetallic Pt-Pd Hollow Nanoparticles with Dendritic Shells by Selective Chemical Etching
    Wang, Liang; Yamauchi, Yusuke
    Journal of the American Chemical Society (2013), 135 (45), 16762-16765CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    We report a facile synthesis of Pt-Pd bimetallic nanoparticles, named "metallic nanocages", with a hollow interior and porous dendritic shell. This synthesis is easily achieved by selective chem. etching of Pd cores from dendritic Pt-on-Pd nanoparticles. The obtained Pt-Pd nanocages show superior catalytic activity for methanol oxidn. reaction compared to other Pt-based materials reported previously.
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    Chen, J.; Lim, B.; Lee, E. P.; Xia, Y. Shape-controlled Synthesis of Platinum Nanocrystals for Catalytic and Electrocatalytic Applications. Nano Today 2009, 4, 81– 95,  DOI: 10.1016/j.nantod.2008.09.002
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    Shape-controlled synthesis of platinum nanocrystals for catalytic and electrocatalytic applications
    Chen, Jingyi; Lim, Byungkwon; Lee, Eric P.; Xia, Younan
    Nano Today (2009), 4 (1), 81-95CODEN: NTAOCG; ISSN:1748-0132. (Elsevier Ltd.)
    A review. Platinum has been widely used in many applications, esp. for catalysis and fuel cell technol. due to its ability to maneuver both oxidn. and redn. reactions. In addn. to size, the shape or morphol. of a Pt nanocrystal provides a sensitive knob for tuning its catalytic and electrocatalytic properties. A no. of chem. routes have been developed to produce Pt nanocrystals with well-defined and controllable shapes to improve their performance in terms of catalytic activity and selectivity. Conventional polyhedrons (e.g., cubes, octahedrons, and tetrahedrons) and their overgrown structures (e.g., multipods) have all been obtained in reasonably high yields, as well as some unconventional shapes (e.g., tetrahexahedrons). Compared to com. available Pt catalysts, these well-defined nanocrystals exhibit greatly enhanced activity and selectivity for a range of reactions.
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    Cuenya, B. R. Synthesis and Catalytic Properties of Metal Nanoparticles: Size, Shape, Support, Composition, and Oxidation State Effects. Thin Solid Films 2010, 518, 3127– 3150,  DOI: 10.1016/j.tsf.2010.01.018
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    Synthesis and catalytic properties of metal nanoparticles: size, shape, support, composition, and oxidation state effects
    Cuenya, Beatriz Roldan
    Thin Solid Films (2010), 518 (12), 3127-3150CODEN: THSFAP; ISSN:0040-6090. (Elsevier B.V.)
    Review. Exciting new opportunities are emerging in the field of catalysis based on nanotechnol. approaches. A new understanding and mastery of catalysis could have broad societal impacts, since about 80% of the processes in the chem. industry depend on catalysts to work efficiently. Efforts in surface science have led to the discovery of new heterogeneous catalysts, however, until recently the only way to develop new or improved catalysts was by empirical testing in trial-and-error expts. This time-consuming and costly procedure is now rapidly being replaced by rational design methods that utilize fundamental knowledge of catalysts at the nanoscale. The advent of nanoscience and nanotechnol. is providing the ability to create controlled structures and geometries to investigate and optimize a broad range of catalytic processes. As a result, researchers are obtaining fundamental insight into key features that influence the activity, selectivity, and lifetime of nanocatalysts. This review article examines several new findings as well as current challenges in the field of nanoparticle based catalysis, including the role played by the particle structure and morphol. (size and shape), its chem. compn. and oxidn. state, and the effect of the cluster support.
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    Shang, C.; Hong, W.; Wang, J.; Wang, E. Carbon Supported Trimetallic Nickel–Palladium–Gold Hollow Nanoparticles with Superior Catalytic Activity for Methanol Electrooxidation. J. Power Sources 2015, 285, 12– 15,  DOI: 10.1016/j.jpowsour.2015.03.092
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    Carbon supported trimetallic nickel-palladium-gold hollow nanoparticles with superior catalytic activity for methanol electrooxidation
    Shang, Changshuai; Hong, Wei; Wang, Jin; Wang, Erkang
    Journal of Power Sources (2015), 285 (), 12-15CODEN: JPSODZ; ISSN:0378-7753. (Elsevier B.V.)
    Ni nanoparticles (NPs) were prepd. in an aq. soln. by using Na borohydride as reducing agent. With Ni NPs as the sacrificial template, hollow NiPdAu NPs are successfully prepd. via partly galvanic displacement reaction between suitable metal precursors and Ni NPs. The as-synthesized hollow NiPdAu NPs can well dispersed on the C substrate. TEM, x-ray diffraction and inductively coupled plasma mass spectrometry are taken to analyze the morphol., structure and compn. of the as-synthesized catalysts. The prepd. catalysts show superior catalytic activity and stability for MeOH electrooxidn. in alk. media compared with com. Pd/C and Pt/C. Catalysts prepd. in this work show great potential to be anode catalysts in direct MeOH fuel cells.
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    Xing, R.; Zhou, T.; Zhou, Y.; Ma, R.; Liu, Q.; Luo, J.; Wang, J. Creation of Triple Hierarchical Micro-Meso-Macroporous N-doped Carbon Shells with Hollow Cores Toward the Electrocatalytic Oxygen Reduction Reaction. Nano-Micro Lett. 2018, 10, 3,  DOI: 10.1007/s40820-017-0157-1
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    Creation of triple hierarchical micro-meso-macroporous N-doped carbon shells with hollow cores toward the electrocatalytic oxygen reduction reaction
    Xing, Ruohao; Zhou, Tingsheng; Zhou, Yao; Ma, Ruguang; Liu, Qian; Luo, Jun; Wang, Jiacheng
    Nano-Micro Letters (2018), 10 (1), 3/1-3/14CODEN: NLAEBV; ISSN:2150-5551. (Nano-Micro Letters)
    A series of triple hierarchical micro-mesomacroporous N-doped carbon shells with hollow cores have been successfully prepd. via etching N-doped hollow carbon spheres with CO2 at high temps. The surface areas, total pore vols. and micropore percentages of the CO2-activated samples evidently increase with increasing activation temp. from 800 to 950 °C, while the N contents show a contrary trend from 7.6 to 3.8 at%. The pyridinic and graphitic nitrogen groups are dominant among various N-contg. groups in the samples. The 950 °C-activated sample (CANHCS-950) has the largest surface area (2072 m2 g-1), pore vol. (1.96 cm3 g-1), hierarchical micro-mesopore distributions (1.2, 2.6 and 6.2 nm), hollow macropore cores (∼91 nm) and highest relative content of pyridinic and graphitic N groups. This triple micro-meso-macropore system could synergistically enhance the activity because macropores could store up the reactant, mesopores could reduce the transport resistance of the reactants to the active sites, and micropores could be in favor of the accumulation of ions. Therefore, the CANHCS-950 with optimized structure shows the optimal and comparable oxygen redn. reaction (ORR) activity but superior methanol tolerance and long-term durability to com. Pt/C with a 4e-- dominant transfer pathway in alk. media. These excellent properties in combination with good stability and recyclability make CANHCSs among the most promising metal-free ORR electrocatalysts reported so far in practical applications.
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    Prieto, G.; Tüysüz, H.; Duyckaerts, N.; Knossalla, J.; Wang, G.-H.; Schüth, F. Hollow Nano- and Microstructures as Catalysts. Chem. Rev. 2016, 116, 14056– 14119,  DOI: 10.1021/acs.chemrev.6b00374
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    Hollow Nano- and Microstructures as Catalysts
    Prieto, Gonzalo; Tueysuez, Harun; Duyckaerts, Nicolas; Knossalla, Johannes; Wang, Guang-Hui; Schueth, Ferdi
    Chemical Reviews (Washington, DC, United States) (2016), 116 (22), 14056-14119CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    Catalysis is at the core of almost every established and emerging chem. process and also plays a central role in the quest for novel technologies for the sustainable prodn. and conversion of energy. Particularly since the early 2000s, a great surge of interest exists in the design and application of micro- and nanometer-sized materials with hollow interiors as solid catalysts. This review provides an updated and crit. survey of the ever-expanding material architectures and applications of hollow structures in all branches of catalysis, including bio-, electro-, and photocatalysis. First, the main synthesis strategies toward hollow materials are succinctly summarized, with emphasis on the (regioselective) incorporation of various types of catalytic functionalities within their different subunits. The principles underlying the scientific and technol. interest in hollow materials as solid catalysts, or catalyst carriers, are then comprehensively reviewed. Aspects covered include the stabilization of catalysts by encapsulation, the introduction of mol. sieving or stimuli-responsive "auxiliary" functionalities, as well as the single-particle, spatial compartmentalization of various catalytic functions to create multifunctional (bio)catalysts. Examples are also given on the applications which hollow structures find in the emerging fields of electro- and photocatalysis, particularly in the context of the sustainable prodn. of chem. energy carriers. Finally, a crit. perspective is provided on the plausible evolution lines for this thriving scientific field, as well as the main practical challenges relevant to the reproducible and scalable synthesis and utilization of hollow micro- and nanostructures as solid catalysts.
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    Haes, A. J.; Zou, S.; Schatz, G. C.; Duyne, R. P. V. A Nanoscale Optical Biosensor: The Long Range Distance Dependence of the Localized Surface Plasmon Resonance of Noble Metal Nanoparticles. J. Phys. Chem. B 2004, 108, 109– 116,  DOI: 10.1021/jp0361327
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    A Nanoscale Optical Biosensor: The Long Range Distance Dependence of the Localized Surface Plasmon Resonance of Noble Metal Nanoparticles
    Haes, Amanda J.; Zou, Shengli; Schatz, George C.; Van Duyne, Richard P.
    Journal of Physical Chemistry B (2004), 108 (1), 109-116CODEN: JPCBFK; ISSN:1520-6106. (American Chemical Society)
    The elucidation of the long range distance dependence of the localized surface plasmon resonance (LSPR) of surface-confined noble metal nanoparticles is the aim of this work. It was suspected that the linear distance dependence found in Me(CH2)xSH self-assembled monolayer (SAM) formation was the thin shell limit of a longer range, nonlinear dependence. To verify this, multilayer SAM shells based on the interaction of HOOC(CH2)10SH and Cu2+ were assembled onto surface-confined noble metal nanoparticles and were monitored using UV-visible spectroscopy. Measurement of the LSPR extinction peak shift vs. no. of layers and adsorbate thickness is nonlinear and has a sensing range that is dependent on the compn., shape, in-plane width, and out-of-plane height of the nanoparticles. Theor. calcns. based on an accurate electrodynamics description of the metal nanoparticle plus surrounding layered material indicate plasmon resonance wavelength shifts that are in excellent agreement with the measurements. The calcns. show that the sensing range is detd. by falloff of the av. induced elec. field around the nanoparticle. This detailed set of expts. coupled with an excellent theory vs. expt. comparison prove that the sensing capabilities of noble metal nanoparticles can be size tuned to match the dimensions of biol. and chem. analytes by adjusting the aforementioned properties. The optimization of the LSPR nanosensor for a specific analyte will significantly improve an already sensitive nanoparticle-based sensor.
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    Polshettiwar, V.; Varma, R. S. Green Chemistry by Nano-Catalysis. Green Chem. 2010, 12, 743– 754,  DOI: 10.1039/b921171c
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    Green chemistry by nano-catalysis
    Polshettiwar, Vivek; Varma, Rajender S.
    Green Chemistry (2010), 12 (5), 743-754CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
    A review. Nano-materials are important in many diverse areas, from basic research to various applications in electronics, biochem. sensors, catalysis and energy. They have emerged as sustainable alternatives to conventional materials, as robust high surface area heterogeneous catalysts and catalyst supports. The nano-sized particles increase the exposed surface area of the active component of the catalyst, thereby enhancing the contact between reactants and catalyst dramatically and mimicking the homogeneous catalysts. This review focuses on the use of nano-catalysis for green chem. development including the strategy of using microwave heating with nano-catalysis in benign aq. reaction media which offers an extraordinary synergistic effect with greater potential than these three components in isolation. To illustrate the proof-of-concept of this "green and sustainable" approach, representative examples are discussed in this article.
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    Sawoo, S.; Srimani, D.; Dutta, P.; Lahiri, R.; Sarkar, A. Size Controlled Synthesis of Pd Nanoparticles in Water and Their Catalytic Application in C–C Coupling Reactions. Tetrahedron 2009, 65, 4367– 4374,  DOI: 10.1016/j.tet.2009.03.062
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    Size controlled synthesis of Pd nanoparticles in water and their catalytic application in C-C coupling reactions
    Sawoo, Sudeshna; Srimani, Dipankar; Dutta, Piyali; Lahiri, Rima; Sarkar, Amitabha
    Tetrahedron (2009), 65 (22), 4367-4374CODEN: TETRAB; ISSN:0040-4020. (Elsevier Ltd.)
    Catalytically active Pd nanoparticles have been synthesized in water by redn. of Pd(II) with a Fischer carbene complex where polyethylene glycol (PEG) was used as stabilizer. PEG mols. wrap around the nanoparticles to impart stability and prevent agglomeration, yet leave enough surface area available on the nanoparticle for catalytic activity. This method is superior to others in terms of rapid generation and stabilization of Pd nanoparticles in water with a cheap, readily available PEG stabilizer. The size of the nanoparticles generated can be controlled by the concn. of PEG in water medium. The size decreased with the increase in the PEG: Pd ratio. This aq. nano-sized Pd is a highly efficient catalyst for Suzuki, Heck, Sonogashira, and Stille reaction. Water is used as the only solvent for the coupling reactions.
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    Budarin, V. L.; Shuttleworth, P. S.; Clark, J. H.; Luque, R. Industrial Applications of C-C Coupling Reactions. Curr. Org. Synth. 2010, 7, 614– 627,  DOI: 10.2174/157017910794328529
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    Industrial applications of C-C coupling reactions
    Budarin, Vitaliy L.; Shuttleworth, Peter S.; Clark, James H.; Luque, Rafael
    Current Organic Synthesis (2010), 7 (6), 614-627CODEN: COSUC2; ISSN:1570-1794. (Bentham Science Publishers Ltd.)
    A review. Arom. substitutions are a very important class of reaction for both the fine chem. and pharmaceutical industries. The use of palladium as a catalyst for these types of reactions is common during the research stages of product development. Its desirable criteria include high selectivity, being compatible with many types of functional groups, typical use without protection groups and strong bases, and introduction at relatively late stages of the total synthesis. However, its use is less common in large-scale manuf. due to their cost and availability of arom. halides at scale. In addn., palladium contamination of pharmaceutical products is 10 ppm or less that is difficult to achieve without strenuous and typically wastefully remediation strategies in place. In this contribution, the authors gave an overview of the use of a range of greener methodologies and catalysts trends in C-C couplings at industrial scale, with selected examples of current compds. industrially produced via such reactions.
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    Luongo, K.; Sine, A.; Bhansali, S. Development of a Highly Sensitive Porous Si-Based Hydrogen Sensor Using Pd Nano-Structures. Sens. Actuators, B 2005, 111-112, 125– 129,  DOI: 10.1016/j.snb.2005.06.056
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    Development of a highly sensitive porous Si-based hydrogen sensor using Pd nano-structures
    Luongo, Kevin; Sine, Altagrace; Bhansali, Shekhar
    Sensors and Actuators, B: Chemical (2005), 111-112 (), 125-129CODEN: SABCEB; ISSN:0925-4005. (Elsevier B.V.)
    A novel, resistance-based porous Si sensor with Pd nano-structures as H sensing layer is presented. The sensor operates at room temp. p-Type Si substrate is subjected to porous Si etching. The substrate is then coated with a thin layer of Pd and annealed at 900°. This results in some Pd getting oxidized on porous Si and a thin PdO layer forms on the surface of the substrate. The sensor was tested at 0-1.5% H. The sensor responded in real time. Unlike conventional thin film-based resistive H sensors this sensor showed an inverse relation between increased H concn. vs. resistance. The mechanism driving the changed output is discussed.
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    Zhou, C.; Szpunar, J. A. Hydrogen Storage Performance in Pd/Graphene Nanocomposites. ACS Appl. Mater. Interfaces 2016, 8, 25933– 25940,  DOI: 10.1021/acsami.6b07122
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    Hydrogen Storage Performance in Pd/Graphene Nanocomposites
    Zhou, Chunyu; Szpunar, Jerzy A.
    ACS Applied Materials & Interfaces (2016), 8 (39), 25933-25940CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
    The authors have developed a Pd-graphene nanocomposite for hydrogen storage. The spherically shaped Pd nanoparticles of 5-45 nm in size are homogeneously distributed over the graphene matrix. This new hydrogen storage system has favorable features like desirable hydrogen storage capacity, ambient conditions of hydrogen uptake, and low temp. of hydrogen release. At a hydrogen charging pressure of 50 bar, the material could yield a gravimetric d. of 6.7% in the 1% Pd/graphene nanocomposite. As the authors increased the applied pressure to 60 bar, the hydrogen uptake capacity reached 8.67% in the 1% Pd/graphene nanocomposite and 7.16% in the 5% Pd/graphene nanocomposite. This system allows storage of hydrogen in amts. that exceed the capacity of the gravimetric target announced by the U.S. Department of Energy (DOE).
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    Nørskov, J. K.; Bligaard, T.; Rossmeisl, J.; Christensen, C. H. Towards the Computational Design of Solid Catalysts. Nat. Chem. 2009, 1, 37– 46,  DOI: 10.1038/nchem.121
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    Towards the computational design of solid catalysts
    Norskov, J. K.; Bligaard, T.; Rossmeisl, J.; Christensen, C. H.
    Nature Chemistry (2009), 1 (1), 37-46CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)
    A review; over the past decade the theor. description of surface reactions has undergone a radical development. Advances in d. functional theory mean it is now possible to describe catalytic reactions at surfaces with the detail and accuracy required for computational results to compare favorably with expts. Theor. methods can be used to describe surface chem. reactions in detail and to understand variations in catalytic activity from one catalyst to another. Here, we review the first steps towards using computational methods to design new catalysts. Examples include screening for catalysts with increased activity and catalysts with improved selectivity. We discuss how, in the future, such methods may be used to engineer the electronic structure of the active surface by changing its compn. and structure.
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    Xia, X.; Wang, Y.; Ruditskiy, A.; Xia, Y. Galvanic Replacement: A Simple and Versatile Route to Hollow Nanostructures with Tunable and Well-Controlled Properties. Adv. Mater. 2013, 25, 6313– 6333,  DOI: 10.1002/adma.201302820
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    25th Anniversary Article: Galvanic replacement: A simple and versatile route to hollow nanostructures with tunable and well-controlled properties
    Xia, Xiaohu; Wang, Yi; Ruditskiy, Aleksey; Xia, Younan
    Advanced Materials (Weinheim, Germany) (2013), 25 (44), 6313-6333CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Review. This article provides a progress report on the use of galvanic replacement for generating complex hollow nanostructures with tunable and well-controlled properties. We begin with a brief account of the mechanistic understanding of galvanic replacement, specifically focused on its ability to engineer the properties of metal nanostructures in terms of size, compn., structure, shape, and morphol. We then discuss a no. of important concepts involved in galvanic replacement, including the facet selectivity involved in the dissoln. and deposition of metals, the impacts of alloying and dealloying on the structure and morphol. of the final products, and methods for promoting or preventing a galvanic replacement reaction. We also illustrate how the capability of galvanic replacement can be enhanced to fabricate nanomaterials with complex structures and/or compns. by coupling with other processes such as co-redn. and the Kirkendall effect. Finally, we highlight the use of such novel metal nanostructures fabricated via galvanic replacement for applications ranging from catalysis to plasmonics and biomedical research, and conclude with remarks on prospective future directions.
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    Vanrenterghem, B.; Papaderakis, A.; Sotiropoulos, S.; Tsiplakides, D.; Balomenou, S.; Bals, S.; Breugelmans, T. The Reduction of Benzylbromide at Ag-Ni Deposits Prepared by Galvanic Replacement. Electrochim. Acta 2016, 196, 756– 768,  DOI: 10.1016/j.electacta.2016.02.135
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    The reduction of benzylbromide at Ag-Ni deposits prepared by galvanic replacement
    Vanrenterghem, B.; Papaderakis, A.; Sotiropoulos, S.; Tsiplakides, D.; Balomenou, S.; Bals, S.; Breugelmans, T.
    Electrochimica Acta (2016), 196 (), 756-768CODEN: ELCAAV; ISSN:0013-4686. (Elsevier Ltd.)
    A two-step procedure was applied to prep. bimetallic Ag-Ni glassy C supported catalysts (Ag-Ni/GC). First Ni layers were prepd. by electrodeposition in an aq. deaerated Ni chloride + Ni sulfamate + boric acid soln. Second, the partial replacement of Ni layers by Ag was achieved upon immersion of the latter in solns. contg. Ag nitrate. Three different pretreatment protocols were used after prepn. of the Ag/Ni deposits; as prepd., cathodised in alkali and scanned in acid. After the pretreatment the surface was characterized by spectroscopy techniques (SEM and energy dispersive x-ray) and electrochem. in an alkali NaOH soln. through cyclic voltammetry (CV). Afterwards the modified electrodes were tested for the redn. of benzylbromide in MeCN solns. by using CV and show improved activity compared to bulk Ag electrode. The highest activity towards benzylbromide redn. was obsd. for pre-cathodised Ag-Ni electrodes. A final stage of the research focuses on the development of a practical Ag/Ni foam catalyst for the redn. of benzylbromide. Due to the high electrochem. active surface area of Ag/Ni foam, a higher conversion of benzyl bromide was obtained in comparison with bulk Ag.
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    Sui, N.; Wang, K.; Shan, X.; Bai, Q.; Wang, L.; Xiao, H.; Liu, M.; Colvin, V. L.; Yu, W. W. Facile Synthesis of Hollow Dendritic Ag/Pt Alloy Nanoparticles for Enhanced Methanol Oxidation Efficiency. Dalton Trans. 2017, 46, 15541– 15548,  DOI: 10.1039/C7DT03671J
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    Facile synthesis of hollow dendritic Ag/Pt alloy nanoparticles for enhanced methanol oxidation efficiency
    Sui, Ning; Wang, Ke; Shan, Xinyao; Bai, Qiang; Wang, Lina; Xiao, Hailian; Liu, Manhong; Colvin, Vicki L.; Yu, William W.
    Dalton Transactions (2017), 46 (44), 15541-15548CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)
    Hollow dendritic Ag/Pt alloy nanoparticles were synthesized by a double template method: Ag nanoparticles as the hard template to obtain hollow spheres by a galvanic replacement reaction between PtCl62- and metallic Ag and surfactant micelles (Brij58) as the soft template to generate porous dendrites. The formation of a Ag/Pt alloy phase was confirmed by XRD and HRTEM. Elemental mapping and line scanning revealed the formation of the hollow architecture. We studied the effects of the Ag/Pt ratio, surfactant and reaction temp. on the morphol. We explored the formation process of hollow dendritic Ag/Pt nanoparticles by tracking the morphologies of the nanostructures formed at different stages. In order to improve the electrocatalytic property, we controlled the size of the nanoparticles and the thickness of the shell by adjusting the amt. of the precursor. We found that these Ag/Pt alloy nanoparticles exhibited high activity (440 mA/mg) and stability as an electrocatalyst for catalyzing MeOH oxidn.
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  19. 19
    Richard-Daniel, J.; Boudreau, D. Enhancing Galvanic Replacement in Plasmonic Hollow Nanoparticles: Understanding the Role of the Speciation of Metal Ion Precursors. ChemNanoMat 2020, 6, 907– 915,  DOI: 10.1002/cnma.202000158
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    19
    Enhancing Galvanic Replacement in Plasmonic Hollow Nanoparticles: Understanding the Role of the Speciation of Metal Ion Precursors
    Richard-Daniel, Josee; Boudreau, Denis
    ChemNanoMat (2020), 6 (6), 907-915CODEN: CHEMSB; ISSN:2199-692X. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Hollow nanostructures offer great potential for plasmonic applications due to their strong and highly tunable localized surface plasmon resonance. The relationship between the plasmonic properties and geometry of hollow nanoparticles, such as core-shell size ratio, concentricity of the cavity and porosity of the wall, is well documented. Nanoscale galvanic replacement provides a simple, versatile and powerful route for the prepn. of such hollow structures. Here we demonstrate how the efficiency of reductant-assisted galvanic replacement processes can be enhanced by controlling the degree of hydration and hydrolysis of the metal ion precursor using pH and pL as key control parameters (by analogy to pH, the letter p in the expression pL is used to indicate the decimal cologarithm assocd. with the concn. of the ligand L). Adjusting precursor speciation prior to the sacrificial template's hollowing process offers a new strategy to tune the morphol. and optical properties of plasmonic hollow nanostructures.
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  20. 20
    Wang, M.; Zhang, W.; Wang, J.; Wexler, D.; Poynton, S. D.; Slade, R. C. T.; Liu, H.; Winther-Jensen, B.; Kerr, R.; Shi, D.; Chen, J. PdNi Hollow Nanoparticles for Improved Electrocatalytic Oxygen Reduction in Alkaline Environments. ACS Appl. Mater. Interfaces 2013, 5, 12708– 12715,  DOI: 10.1021/am404090n
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    PdNi Hollow Nanoparticles for Improved Electrocatalytic Oxygen Reduction in Alkaline Environments
    Wang, Meng; Zhang, Weimin; Wang, Jiazhao; Wexler, David; Poynton, Simon D.; Slade, Robert C. T.; Liu, Huakun; Winther-Jensen, Bjorn; Kerr, Robert; Shi, Dongqi; Chen, Jun
    ACS Applied Materials & Interfaces (2013), 5 (23), 12708-12715CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
    Pd-Ni hollow nanoparticles were synthesized via a modified galvanic replacement method using Ni nanoparticles as sacrificial templates in an aq. medium. X-ray diffraction and TEM show that the as-synthesized nanoparticles are alloyed nanostructures and have hollow interiors with an av. particle size of 30 nm and shell thickness of 5 nm. Compared with the com. available Pt/C or Pd/C catalysts, the synthesized PdNi/C has superior electrocatalytic performance towards the O redn. reaction, which makes it a promising electrocatalyst for alk. anion exchange membrane fuel cells and alkali-based air-batteries. The electrocatalyst is finally examd. in a H2/O2 alk. anion exchange membrane fuel cell; such electrocatalysts could work in a real fuel cell application as a more efficient catalyst than state-of-the-art com. available Pt/C.
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    Li, C.; Su, Y.; Lv, X.; Shi, H.; Yang, X.; Wang, Y. Enhanced Ethanol Electrooxidation of Hollow Pd Nanospheres Prepared by Galvanic Exchange Reactions. Mater. Lett. 2012, 69, 92– 95,  DOI: 10.1016/j.matlet.2011.11.054
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    21
    Enhanced ethanol electrooxidation of hollow Pd nanospheres prepared by galvanic exchange reactions
    Li, Cuiling; Su, Yi; Lv, Xiangyu; Shi, Hongjun; Yang, Xiangguang; Wang, Yujiang
    Materials Letters (2012), 69 (), 92-95CODEN: MLETDJ; ISSN:0167-577X. (Elsevier B.V.)
    In this work hollow Pd nanospheres were successfully synthesized by using galvanic replacement of facile synthesized Cu2O nanospheres with palladium for the first time. The SEM showed the hollow structure of Pd nanospheres and the XRD anal. proved the successful prepn. of Pd. This method is surfactant-free, and well-dispersed hollow Pd nanospheres can be obtained through this route. It was found that the hollow Pd nanospheres showed good electrochem. properties and could be used as catalysts in DEFCs. From cyclic voltammograms, the onset potential of hollow Pd nanospheres shifted neg. by 100 mV and the peak current of hollow Pd nanospheres was about two times higher than that of solid Pd nanospheres.
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    Niu, W.; Li, Z.-Y.; Shi, L.; Liu, X.; Li, H.; Han, S.; Chen, J.; Xu, G. Seed-Mediated Growth of Nearly Monodisperse Palladium Nanocubes with Controllable Sizes. Cryst. Growth Des. 2008, 8, 4440– 4444,  DOI: 10.1021/cg8002433
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    Seed-Mediated Growth of Nearly Monodisperse Palladium Nanocubes with Controllable Sizes
    Niu, Wenxin; Li, Zhi-Yuan; Shi, Lihong; Liu, Xiaoqing; Li, Haijuan; Han, Shuang; Chen, Jiuan; Xu, Guobao
    Crystal Growth & Design (2008), 8 (12), 4440-4444CODEN: CGDEFU; ISSN:1528-7483. (American Chemical Society)
    Nearly monodisperse Pd nanocubes with controllable sizes were synthesized through a seed-mediated growth approach. By using Pd nanocubes of 22 nm in size as seeds, the morphol. of the as-grown nanostructures was fixed as single-cryst., which enabled one to rationally tune the size of Pd nanocubes. The formation mechanism of initial 22 nm nanocubes was also discussed. The size-dependent surface plasmon resonance properties of the as-synthesized Pd nanocubes were studied. Compared with previous methods, the yield, monodispersity, perfection of the shape formation, and the range of size control of these nanocubes are all improved. These Pd nanocubes may have potential interests in surface-enhanced Raman scattering, sensors, catalysis, study of size-dependent properties, and fabrication of high-order structures.
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  23. 23
    Wen, X.; Lerch, S.; Wang, Z.; Aboudiab, B.; Tehrani-Bagha, A. R.; Olsson, E.; Moth-Poulsen, K. Synthesis of Palladium Nanodendrites Using a Mixture of Cationic and Anionic Surfactants. Langmuir 2020, 36, 1745– 1753,  DOI: 10.1021/acs.langmuir.9b03804
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    Synthesis of Palladium Nanodendrites Using a Mixture of Cationic and Anionic Surfactants
    Wen, Xin; Lerch, Sarah; Wang, Zhihang; Aboudiab, Bassem; Tehrani-Bagha, Ali Reza; Olsson, Eva; Moth-Poulsen, Kasper
    Langmuir (2020), 36 (7), 1745-1753CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)
    Surfactants are used widely to control the synthesis of shaped noble-metal nanoparticles. In this work, a mixt. of hexadecyltrimethylammonium bromide (CTAB), a cationic surfactant; sodium oleate (NaOL), an anionic surfactant; palladium chloride; and a reducing agent were used in the seed-mediated synthesis of palladium nanoparticles. By controlling the surfactant mixt. ratio, we initially discovered that palladium nanodendrites with narrow size distribution were formed instead of the traditional nanocubes, synthesized with only CTAB. In order to investigate the optimal ratio to produce Pd nanodendrites with a high yield and narrow size distribution, samples synthesized with multiple molar ratios of the two surfactants were prepd. and studied by transmission electron microscopy, dynamic light scattering, conductance, and UV-visible spectroscopy. We propose that the addn. of NaOL alters the arrangement of surfactants on the Pd seed surface, leading to a new pattern of growth and aggregation. By studying the nanodendrite growth over time, we identified the redn. period of Pd2+ ions and the formation period of the nanodendrites. Our further expts., including the replacement of CTAB with hexadecyltrimethylammonium chloride (CTAC) and the replacement of NaOL with sodium stearate, showed that CTA+ ions in CTAB and OL- ions in NaOL play the main roles in the formation of nanodendrites. The formation of palladium nanodendrites was robust and achieved with a range of temps., pH and mixing speeds.
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    Niu, W.; Zhang, L.; Xu, G. Shape-Controlled Synthesis of Single-Crystalline Palladium Nanocrystals. ACS Nano 2010, 4, 1987– 1996,  DOI: 10.1021/nn100093y
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    Shape-Controlled Synthesis of Single-Crystalline Palladium Nanocrystals
    Niu, Wenxin; Zhang, Ling; Xu, Guobao
    ACS Nano (2010), 4 (4), 1987-1996CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)
    A versatile method for selectively synthesizing single-cryst. rhombic dodecahedral, cubic, and octahedral palladium nanocrystals, as well as their derivs. with varying degrees of edge- and corner-truncation, was reported for the first time. This is also the first report regarding the synthesis of rhombic dodecahedral palladium nanocrystals. All the nanocrystals were readily synthesized by a seed-mediated method with cetyltrimethylammonium bromide as surfactant, KI as additive, and ascorbic acid as reductant. At the same ascorbic acid concn., a series of palladium nanocrystals with varying shapes were obtained through manipulation of the concn. of KI and the reaction temp. The formation of different palladium facets were correlated with their growth conditions. In the absence of KI, the {100} palladium facets are favored. In the presence of KI, the concn. of KI and the reaction temp. play an important role on the formation of different palladium facets. The {110} palladium facets are favored at relatively high temps. and medium KI concns. The {111} palladium facets are favored at relatively low temps. and medium KI concns. The {100} palladium facets are favored at either very low or relatively high KI concns. These correlations were explained in terms of surface-energy and growth kinetics. These results provide a basis for gaining mechanistic insights into the growth of well-faceted metal nanostructures.
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    Lee, C.-L.; Tseng, C.-M.; Wu, R.-B.; Wu, C.-C.; Syu, S.-C. Catalytic characterization of hollow silver/palladium nanoparticles synthesized by a displacement reaction. Electrochim. Acta 2009, 54, 5544– 5547,  DOI: 10.1016/j.electacta.2009.04.056
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    Catalytic characterization of hollow silver/palladium nanoparticles synthesized by a displacement reaction
    Lee, Chien-Liang; Tseng, Chun-Ming; Wu, Rong-Bing; Wu, Chen-Chung; Syu, Shu-Ciao
    Electrochimica Acta (2009), 54 (23), 5544-5547CODEN: ELCAAV; ISSN:0013-4686. (Elsevier B.V.)
    Hollow Ag/Pd nanoparticles were successfully prepd. by a galvanic displacement reaction, in which a small amt. of Pd(NO3)2 is allowed to react with previously synthesized Ag nanoparticles that act as templates. The resulting hollow Ag/Pd (Ag/Pdhollow) nanoparticles are icosahedral and decahedral in structure. The kinetics of electroless Cu deposition (ECD) catalyzed by these bimetallic (Ag/Pdhollow) nanoparticles are analyzed using an electrochem. quartz crystal microbalance (EQCM). These Ag/Pdhollow nanoparticles have better catalytic activities than monometallic Ag and Pd nanoparticles. Also, the catalytic activities of these hollow nanoparticles in the ECD bath can be controlled by tuning their alloy ratios in a suitable manner.
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    Chen, D.; Cui, P.; Liu, H.; Yang, J. Catalytic Characterization of Hollow Silver/Palladium Nanoparticles Synthesized by a Displacement Reaction. Electrochim. Acta 2015, 153, 461– 467,  DOI: 10.1016/j.electacta.2014.12.016
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    Heterogeneous nanocomposites composed of silver sulfide and hollow structured Pd nanoparticles with enhanced catalytic activity toward formic acid oxidation
    Chen, Dong; Cui, Penglei; Liu, Hui; Yang, Jun
    Electrochimica Acta (2015), 153 (), 461-467CODEN: ELCAAV; ISSN:0013-4686. (Elsevier Ltd.)
    Nanocomposites consisting semiconductor and noble metal domains are of great interest for their synergistic effect-based enhanced properties in a given application. Herein, we demonstrate a facile approach for the synthesis of heterogeneous nanocomposites consisting of silver sulfide (Ag2S) and hollow structured Pd nanoparticles (hPd). It begins with the prepn. of core-shell nanoparticles with an Ag core and an alloy Ag/Pd shell in an org. solvent via galvanic replacement reaction (GRR) between Ag seed particles pre-synthesized and Pd2+ ion precursors. The Ag component is then removed from the core and shell regions of core-shell Ag-Ag/Pd nanoparticles, and converted into Ag2S by elemental sulfur (S). The Ag2S forms the semiconductor domain in the nanocomposite and shares the solid-state interface with the resultant hollow structured Pd nanoparticle. As demonstrated, the Ag2S-hPd nanocomposites exhibit superior catalytic activity and durability for formic acid oxidn., compared to the pure Pd nanoparticles prepd. by oleylamine redn. of Pd ion precursors and com. Pd/C catalyst, due to the electronic coupling between semiconductor and noble metal domains in the nanocomposites. In addn., the structural transformation from core-shell to heterogeneous nanocomposites may provide new opportunities to design and fabricate hybrid nanostructures with interesting physicochem. properties.
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    Ge, J.; Xing, W.; Xue, X.; Liu, C.; Lu, T.; Liao, J. Controllable Synthesis of Pd Nanocatalysts for Direct Formic Acid Fuel Cell (DFAFC) Application: From Pd Hollow Nanospheres to Pd Nanoparticles. J. Phys. Chem. C 2007, 111, 17305– 17310,  DOI: 10.1021/jp073666p
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    Controllable Synthesis of Pd Nanocatalysts for Direct Formic Acid Fuel Cell (DFAFC) Application: From Pd Hollow Nanospheres to Pd Nanoparticles
    Ge, Junjie; Xing, Wei; Xue, Xinzhong; Liu, Changpeng; Lu, Tianhong; Liao, Jianhui
    Journal of Physical Chemistry C (2007), 111 (46), 17305-17310CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    The controllable synthesis of nanosized C-supported Pd catalysts through a surface replacement reaction (SRR) is reported. Depending on the synthesis conditions, the Pd can be formed on Co nanoparticle surfaces in hollow nanospheres or nanoparticles structures. The citrate anion acts as a stabilizer for the nanostructures and protonation of the 3rd carboxyl anion - hence the nanostructure and size of the resulting catalysts are controlled by the pH of the synthesis soln. Pd hollow nanospheres, contg. smaller Pd nanoparticles, supported on C, are formed at pH 9. Highly-dispersed C-supported Pd nanoparticles can be formed at pH ≥10. All catalysts prepd. through this SRR method show enhanced activities for the HCOOH electrooxidn. reaction compared to catalysts obtained through NaBH4 redn.
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    Johnson, N. J. J.; Lam, B.; MacLeod, B. P.; Sherbo, R. S.; Moreno-Gonzalez, M.; Fork, D. K.; Berlinguette, C. P. Facets and Vertices Regulate Hydrogen Uptake and Release in Palladium Nanocrystals. Nat. Mater. 2019, 18, 454– 458,  DOI: 10.1038/s41563-019-0308-5
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    Facets and vertices regulate hydrogen uptake and release in palladium nanocrystals
    Johnson, Noah J. J.; Lam, Brian; MacLeod, Benjamin P.; Sherbo, Rebecca S.; Moreno-Gonzalez, Marta; Fork, David K.; Berlinguette, Curtis P.
    Nature Materials (2019), 18 (5), 454-458CODEN: NMAACR; ISSN:1476-1122. (Nature Research)
    Crystal facets, vertices and edges govern the energy landscape of metal surfaces and thus the chem. interactions on the surface1,2. The facile absorption and desorption of hydrogen at a palladium surface provides a useful platform for defining how metal-solute interactions impact properties relevant to energy storage, catalysis and sensing3-5. Recent advances in operando and in situ techniques have enabled the phase transitions of single palladium nanocrystals to be temporally and spatially tracked during hydrogen absorption6-11. We demonstrate herein that in situ X-ray diffraction can be used to track both hydrogen absorption and desorption in palladium nanocrystals. This ensemble measurement enabled us to delineate distinctive absorption and desorption mechanisms for nanocrystals contg. exclusively (111) or (100) facets. We show that the rate of hydrogen absorption is higher for those nanocrystals contg. a higher no. of vertices, consistent with hydrogen absorption occurring quickly after β-phase nucleation at lattice-strained vertices9,10. Tracking hydrogen desorption revealed initial desorption rates to be nearly tenfold faster for samples with (100) facets, presumably due to the faster recombination of surface hydrogen atoms. These results inspired us to make nanocrystals with a high no. of vertices and (100) facets, which were found to accommodate fast hydrogen uptake and release.
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    Zhang, Q.; Li, W.; Wen, L.-P.; Chen, J.; Xia, Y. Facile Synthesis of Ag Nanocubes of 30 to 70 nm in Edge Length with CF3COOAg as a Precursor. Chem. – Eur. J. 2010, 16, 10234– 10239,  DOI: 10.1002/chem.201000341
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    Facile synthesis of Ag nanocubes of 30 to 70 nm in edge length with CF3COOAg as a precursor
    Zhang, Qiang; Li, Weiyang; Wen, Long-Ping; Chen, Jingyi; Xia, Younan
    Chemistry - A European Journal (2010), 16 (33), 10234-10239, S10234/1-S10234/3CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Ag nanocubes having a 30-70 nm edge length were synthesized by using CF3COOAg as a precursor for elemental silver. By adding a trace amt. of NaSH and HCl in the polyol synthesis, Ag nanocubes were obtained with high quality, high reproducibility, and on a scale of ≤0.19 g per batch for the 70 nm Ag nanocubes. The Ag nanocubes were grew in size at a controllable pace during the synthesis. The linear relationship between the edge length of the Ag nanocubes and position of localized surface plasmon resonance peak provides a simple method for finely tuning and controlling the size of the Ag nanocubes by monitoring the UV/Visible spectra of the reaction at different times.
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    Wang, Y.; Zheng, Y.; Huang, C. Z.; Xia, Y. Synthesis of Ag Nanocubes 18–32 nm in Edge Length: The Effects of Polyol on Reduction Kinetics, Size Control, and Reproducibility. J. Am. Chem. Soc. 2013, 135, 1941– 1951,  DOI: 10.1021/ja311503q
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    Synthesis of Ag Nanocubes 18-32 nm in Edge Length: The Effects of Polyol on Reduction Kinetics, Size Control, and Reproducibility
    Wang, Yi; Zheng, Yiqun; Huang, Cheng Zhi; Xia, Younan
    Journal of the American Chemical Society (2013), 135 (5), 1941-1951CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    This article describes a robust method for the facile synthesis of small Ag nanocubes with edge lengths controlled in the range of 18-32 nm. The success of this new method relies on the substitution of ethylene glycol (EG; the solvent most commonly used in a polyol synthesis) with diethylene glycol (DEG). Owing to the increase in hydrocarbon chain length, DEG possesses a higher viscosity and a lower reducing power relative to EG. As a result, we were able to achieve a nucleation burst in the early stage to generate a large no. of seeds and a relatively slow growth rate thereafter; both factors were crit. to the formation of Ag nanocubes with small sizes and in high purity (>95%). The edge length of the Ag nanocubes could be easily tailored in the range of 18-32 nm by quenching the reaction at different time points. For the first time, we were able to produce uniform sub-20 nm Ag nanocubes in a hydrophilic medium and on a scale of ∼20 mg per batch. It is also worth pointing out that the present protocol was remarkably robust, showing good reproducibility between different batches and even for DEGs obtained from different vendors. Our results suggest that the high sensitivity of synthesis outcomes to the trace amts. of impurities in a polyol, a major issue for reproducibility and scale up synthesis, did not exist in the present system.
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    Fu, B.; Liu, W.; Li, Z. Calculation of the Surface Energy of FCC-Metals with the Empirical Electron Surface Model. Appl. Surf. Sci. 2010, 256, 6899– 6907,  DOI: 10.1016/j.apsusc.2010.04.108
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    Calculation of the surface energy of fcc-metals with the empirical electron surface model
    Fu, Baoqin; Liu, Wei; Li, Zhilin
    Applied Surface Science (2010), 256 (22), 6899-6907CODEN: ASUSEE; ISSN:0169-4332. (Elsevier B.V.)
    The empirical electron surface model (EESM) based on the empirical electron theory and the dangling bond anal. method has been used to establish a database of surface energy for low-index surfaces of fcc-metals such as Al, Mn, Co, Ni, Cu, Pd, Ag, Pt, Au, and Pb. A brief introduction of EESM will be presented in this paper. The calcd. results are in agreement with exptl. and other theor. values. Comparison of the exptl. results and calcn. values shows that the av. relative error is less than 10% and these values show a strong anisotropy. As we predicted, the surface energy of the close-packed plane (1 1 1) is the lowest one of all index surfaces. For low-index planes, the order of the surface energies is γ(1 1 1) < γ(1 0 0) < γ(1 1 0) < γ(2 1 0). It is also found that the dangling bond electron d. and the spatial distribution of covalent bonds have a great influence on surface energy of various index surfaces.
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    Zhang, J.-M.; Ma, F.; Xu, K.-W. Calculation of the Surface Energy of FCC Metals with Modified Embedded-Atom Method. Chin. Phys. 2004, 13, 1082– 1090,  DOI: 10.1088/1009-1963/13/7/020
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    Calculation of the surface energy of fcc metals with modified embedded-atom method
    Zhang, Jian-Min; Ma, Fei; Xu, Ke-wei
    Chinese Physics (Beijing, China) (2004), 13 (7), 1082-1090CODEN: CHPHF4; ISSN:1009-1963. (Chinese Physical Society)
    The surface energies for 38 surfaces of fcc. metals Cu, Ag, Au, Ni, Pd, Pt, Al, Pb, Rh, and Ir were calcd. by the modified embedded-atom method. For Cu, Ag, Ni, Al, Pb, and Ir, the av. values of the surface energies are very close to the polycryst. exptl. data. For all fcc. metals, as predicted, the close-packed (111) surface has the lowest surface energy. The surface energies for the other surfaces increase linearly with increasing angle between the surfaces (hkl) and (111). This can be used to est. the relative values of the surface energy.
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    Huang, Y.; Ferhan, A. R.; Dandapat, A.; Yoon, C. S.; Song, J. E.; Cho, E. C.; Kim, D.-H. A Strategy for the Formation of Gold–Palladium Supra-Nanoparticles from Gold Nanoparticles of Various Shapes and Their Application to High-Performance H2O2 Sensing. J. Phys. Chem. C 2015, 119, 26164– 26170,  DOI: 10.1021/acs.jpcc.5b08423
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    A Strategy for the Formation of Gold-Palladium Supra-Nanoparticles from Gold Nanoparticles of Various Shapes and Their Application to High-Performance H2O2 Sensing
    Huang, Youju; Ferhan, Abdul Rahim; Dandapat, Anirban; Yoon, Chong Seung; Song, Ji Eun; Cho, Eun Chul; Kim, Dong-Hwan
    Journal of Physical Chemistry C (2015), 119 (46), 26164-26170CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    The authors present a new approach for the synthesis of gold (Au)-palladium (Pd) bimetallic supra-nanoparticles in which densely packed anisotropic Pd nanostructures surround a central Au nanoparticle (rod, sphere, cubic shape). They were obtained by Pd crystal growth on Au nanoparticle surfaces which are modified with a mixt. of cetyltrimethylammonium bromide (CTAB) and 5-bromosalicylic acid (5-BrSA). From a comparative study with a Au nanorod (NR) as a seed, the use of the CTAB/5-BrSA mixt. plays a pivotal role in obtaining such unique supra-structures; the Au NR capped with only CTAB resulted in Au core-continuous Pd shell nanoparticles instead. The Au-Pd supra-nanoparticles provide active surface area for electrocatalytic activities higher than that of the Au@Pd continuous shell nanoparticles, displaying outstanding performance for mediator-free electrochem. detection of H2O2.
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  34. 34
    Pekkari, A.; Wen, X.; Orrego, J. R.; Silva, R. R.; Kondo, S.; Olsson, E.; Härelind, H.; Moth-Poulsen, K. Synthesis of Highly Monodisperse Pd Nanoparticles Using a Binary Surfactant Combination and Sodium Oleate as a Reductant. Nanoscale Adv. 2021, 3, 2481– 2487,  DOI: 10.1039/D1NA00052G
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    34
    Synthesis of highly monodisperse Pd nanoparticles using a binary surfactant combination and sodium oleate as a reductant
    Pekkari, Anna; Wen, Xin; Orrego-Hernandez, Jessica; da Silva, Robson Rosa; Kondo, Shun; Olsson, Eva; Haerelind, Hanna; Moth-Poulsen, Kasper
    Nanoscale Advances (2021), 3 (9), 2481-2487CODEN: NAADAI; ISSN:2516-0230. (Royal Society of Chemistry)
    This study presents the synthesis of monodisperse Pd nanoparticles (NPs) stabilized by sodium oleate (NaOL) and hexadecyltrimethylammonium chloride (CTAC). The synthesis was conducted without traditional reductants and Pd-precursors are reduced by NaOL. It was confirmed that the alkyl double bond in NaOL is not the only explanation for the redn. of Pd-precursors since Pd NPs could be synthesized with CTAC and the satd. fatty acid sodium stearate (NaST). A quant. evaluation of the redn. kinetics using UV-Vis spectroscopy shows that Pd NPs synthesized with both stabilizer combinations follow pseudo first-order reaction kinetics, where NaOL provides a faster and more effective redn. of Pd-precursors. The colloidal stabilization of the NP surface by CTAC and NaOL is confirmed by Fourier transform IR (FTIR) and NMR (NMR) anal.
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  1. Patrick Irigo, Nada Yousif, Ian Johnston, Boyan Tatarov, Avinash Yadav, Etelka Chung, Kun Luo, Guogang Ren. Enhancing SERS Spectra through Surface-Doped Nanocluster Substrates: A Numerical Investigation of Plasmonic Silver Coated Pt and Pd Core–Shell-Satellite Structures. The Journal of Physical Chemistry C 2024, Article ASAP.
  2. Xuejiang Liao, Xianzhuo Lao, Ze Li, Likang Yang, Wanneng Ye, Peizhi Guo. Synthesis of Monodispersed Pd Nanoparticles and Ultrathin Twisty Pd Nanowire Networks for Electrooxidation of Ethanol. Langmuir 2024, 40 (17) , 9310-9317. https://doi.org/10.1021/acs.langmuir.4c01028
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  • Abstract

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    Figure 1

    Figure 1. Schematic illustration of the synthesis process of hollow Ag–Ag–Pd nanodendrites and Ag–Ag–Pd nanoboxes. TEM images of Ag nanocubes, hollow Ag–Pd nanodendrites, and hollow Ag–Pd nanoboxes are inserted next to their models.

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    Figure 2

    Figure 2. Low-magnification TEM images (LM), high-magnification images (HM), and selected area electron diffraction patterns (SAED) are shown in sequence. (a) LM, (b) HM, and (c) SAED for Ag nanocubes. (d) LM, (e) HM, and (f) SAED for Ag–Pd nanodendrites. (g) LM, (h) HM, and (i) SAED for Ag–Pd nanoboxes. The average size of each nanoparticle is marked in the corresponding low-magnification TEM image. Histograms of the size distribution are shown in Figure S2 of ESI. (j) Energy-dispersive X-ray spectroscopy (EDS) spectrum of Ag–Pd nanodendrites. (k) EDS spectrum of Ag–Pd nanoboxes.

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    Figure 3

    Figure 3. EDS mapping of hollow Ag–Pd nanoparticles, including a scanning transmission electron microscope (STEM) image of the particles and mappings of Ag, Pd, and Ag–Pd overlay. (a) Nanodendrites, where green is Ag and yellow is Pd. (b) Nanoboxes, where red is Ag and purple is Pd.

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    Figure 4

    Figure 4. X-ray diffraction pattern of Ag-Pd the Ag−Pd nanoboxes and nanodendrites (a) and, a zoomed view of the spectra in the region 37°−48° (b). Reference peaks are shown in green and blue lines.

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    Figure 5

    Figure 5. (a) High-resolution TEM image of an entire hollow Ag–Pd nanobox. The (200) lattice plane is noted by a pair of parallel red lines, and its interplanar spacing is recorded in the image. (b) The corresponding FFT of (a). Interplanar spacings of (111) and (200) lattice planes are marked in the image. (c) The FFT of (d). (d) High-resolution TEM image of the spiky corner, marked by a red square in (a). The (111) lattice plane and its interplanar spacing are recorded. (e) High-resolution TEM image of an entire hollow Ag–Pd nanodendrite. (f) The corresponding FFT of (e). The interplanar spacings of (111) and (200) lattice planes are recorded in the image. (g) The FFT of (h). (h) High-resolution TEM image of the dendrite marked by a red square in (e). The (111) lattice plane is marked by a pair of parallel red lines, and its interplanar spacing is recorded in the image.

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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXjtFGksb8%253D&md5=c8f8418f74f137cceb2ad796ba8527e4
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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXitFGrs7bI&md5=6cfd3d7f964d4e879ee5c7c9856e7b5b
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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xhs1aju7nM&md5=a269c05df7f789532583d991b2b82b73
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      Green chemistry by nano-catalysis
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      A review. Nano-materials are important in many diverse areas, from basic research to various applications in electronics, biochem. sensors, catalysis and energy. They have emerged as sustainable alternatives to conventional materials, as robust high surface area heterogeneous catalysts and catalyst supports. The nano-sized particles increase the exposed surface area of the active component of the catalyst, thereby enhancing the contact between reactants and catalyst dramatically and mimicking the homogeneous catalysts. This review focuses on the use of nano-catalysis for green chem. development including the strategy of using microwave heating with nano-catalysis in benign aq. reaction media which offers an extraordinary synergistic effect with greater potential than these three components in isolation. To illustrate the proof-of-concept of this "green and sustainable" approach, representative examples are discussed in this article.
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      Sawoo, S.; Srimani, D.; Dutta, P.; Lahiri, R.; Sarkar, A. Size Controlled Synthesis of Pd Nanoparticles in Water and Their Catalytic Application in C–C Coupling Reactions. Tetrahedron 2009, 65, 4367– 4374,  DOI: 10.1016/j.tet.2009.03.062
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      Size controlled synthesis of Pd nanoparticles in water and their catalytic application in C-C coupling reactions
      Sawoo, Sudeshna; Srimani, Dipankar; Dutta, Piyali; Lahiri, Rima; Sarkar, Amitabha
      Tetrahedron (2009), 65 (22), 4367-4374CODEN: TETRAB; ISSN:0040-4020. (Elsevier Ltd.)
      Catalytically active Pd nanoparticles have been synthesized in water by redn. of Pd(II) with a Fischer carbene complex where polyethylene glycol (PEG) was used as stabilizer. PEG mols. wrap around the nanoparticles to impart stability and prevent agglomeration, yet leave enough surface area available on the nanoparticle for catalytic activity. This method is superior to others in terms of rapid generation and stabilization of Pd nanoparticles in water with a cheap, readily available PEG stabilizer. The size of the nanoparticles generated can be controlled by the concn. of PEG in water medium. The size decreased with the increase in the PEG: Pd ratio. This aq. nano-sized Pd is a highly efficient catalyst for Suzuki, Heck, Sonogashira, and Stille reaction. Water is used as the only solvent for the coupling reactions.
      >> More from SciFinder ®
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      Development of a highly sensitive porous Si-based hydrogen sensor using Pd nano-structures
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      A novel, resistance-based porous Si sensor with Pd nano-structures as H sensing layer is presented. The sensor operates at room temp. p-Type Si substrate is subjected to porous Si etching. The substrate is then coated with a thin layer of Pd and annealed at 900°. This results in some Pd getting oxidized on porous Si and a thin PdO layer forms on the surface of the substrate. The sensor was tested at 0-1.5% H. The sensor responded in real time. Unlike conventional thin film-based resistive H sensors this sensor showed an inverse relation between increased H concn. vs. resistance. The mechanism driving the changed output is discussed.
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      Zhou, C.; Szpunar, J. A. Hydrogen Storage Performance in Pd/Graphene Nanocomposites. ACS Appl. Mater. Interfaces 2016, 8, 25933– 25940,  DOI: 10.1021/acsami.6b07122
      14
      Hydrogen Storage Performance in Pd/Graphene Nanocomposites
      Zhou, Chunyu; Szpunar, Jerzy A.
      ACS Applied Materials & Interfaces (2016), 8 (39), 25933-25940CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
      The authors have developed a Pd-graphene nanocomposite for hydrogen storage. The spherically shaped Pd nanoparticles of 5-45 nm in size are homogeneously distributed over the graphene matrix. This new hydrogen storage system has favorable features like desirable hydrogen storage capacity, ambient conditions of hydrogen uptake, and low temp. of hydrogen release. At a hydrogen charging pressure of 50 bar, the material could yield a gravimetric d. of 6.7% in the 1% Pd/graphene nanocomposite. As the authors increased the applied pressure to 60 bar, the hydrogen uptake capacity reached 8.67% in the 1% Pd/graphene nanocomposite and 7.16% in the 5% Pd/graphene nanocomposite. This system allows storage of hydrogen in amts. that exceed the capacity of the gravimetric target announced by the U.S. Department of Energy (DOE).
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    15. 15
      Nørskov, J. K.; Bligaard, T.; Rossmeisl, J.; Christensen, C. H. Towards the Computational Design of Solid Catalysts. Nat. Chem. 2009, 1, 37– 46,  DOI: 10.1038/nchem.121
      15
      Towards the computational design of solid catalysts
      Norskov, J. K.; Bligaard, T.; Rossmeisl, J.; Christensen, C. H.
      Nature Chemistry (2009), 1 (1), 37-46CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)
      A review; over the past decade the theor. description of surface reactions has undergone a radical development. Advances in d. functional theory mean it is now possible to describe catalytic reactions at surfaces with the detail and accuracy required for computational results to compare favorably with expts. Theor. methods can be used to describe surface chem. reactions in detail and to understand variations in catalytic activity from one catalyst to another. Here, we review the first steps towards using computational methods to design new catalysts. Examples include screening for catalysts with increased activity and catalysts with improved selectivity. We discuss how, in the future, such methods may be used to engineer the electronic structure of the active surface by changing its compn. and structure.
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    16. 16
      Xia, X.; Wang, Y.; Ruditskiy, A.; Xia, Y. Galvanic Replacement: A Simple and Versatile Route to Hollow Nanostructures with Tunable and Well-Controlled Properties. Adv. Mater. 2013, 25, 6313– 6333,  DOI: 10.1002/adma.201302820
      16
      25th Anniversary Article: Galvanic replacement: A simple and versatile route to hollow nanostructures with tunable and well-controlled properties
      Xia, Xiaohu; Wang, Yi; Ruditskiy, Aleksey; Xia, Younan
      Advanced Materials (Weinheim, Germany) (2013), 25 (44), 6313-6333CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Review. This article provides a progress report on the use of galvanic replacement for generating complex hollow nanostructures with tunable and well-controlled properties. We begin with a brief account of the mechanistic understanding of galvanic replacement, specifically focused on its ability to engineer the properties of metal nanostructures in terms of size, compn., structure, shape, and morphol. We then discuss a no. of important concepts involved in galvanic replacement, including the facet selectivity involved in the dissoln. and deposition of metals, the impacts of alloying and dealloying on the structure and morphol. of the final products, and methods for promoting or preventing a galvanic replacement reaction. We also illustrate how the capability of galvanic replacement can be enhanced to fabricate nanomaterials with complex structures and/or compns. by coupling with other processes such as co-redn. and the Kirkendall effect. Finally, we highlight the use of such novel metal nanostructures fabricated via galvanic replacement for applications ranging from catalysis to plasmonics and biomedical research, and conclude with remarks on prospective future directions.
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    17. 17
      Vanrenterghem, B.; Papaderakis, A.; Sotiropoulos, S.; Tsiplakides, D.; Balomenou, S.; Bals, S.; Breugelmans, T. The Reduction of Benzylbromide at Ag-Ni Deposits Prepared by Galvanic Replacement. Electrochim. Acta 2016, 196, 756– 768,  DOI: 10.1016/j.electacta.2016.02.135
      17
      The reduction of benzylbromide at Ag-Ni deposits prepared by galvanic replacement
      Vanrenterghem, B.; Papaderakis, A.; Sotiropoulos, S.; Tsiplakides, D.; Balomenou, S.; Bals, S.; Breugelmans, T.
      Electrochimica Acta (2016), 196 (), 756-768CODEN: ELCAAV; ISSN:0013-4686. (Elsevier Ltd.)
      A two-step procedure was applied to prep. bimetallic Ag-Ni glassy C supported catalysts (Ag-Ni/GC). First Ni layers were prepd. by electrodeposition in an aq. deaerated Ni chloride + Ni sulfamate + boric acid soln. Second, the partial replacement of Ni layers by Ag was achieved upon immersion of the latter in solns. contg. Ag nitrate. Three different pretreatment protocols were used after prepn. of the Ag/Ni deposits; as prepd., cathodised in alkali and scanned in acid. After the pretreatment the surface was characterized by spectroscopy techniques (SEM and energy dispersive x-ray) and electrochem. in an alkali NaOH soln. through cyclic voltammetry (CV). Afterwards the modified electrodes were tested for the redn. of benzylbromide in MeCN solns. by using CV and show improved activity compared to bulk Ag electrode. The highest activity towards benzylbromide redn. was obsd. for pre-cathodised Ag-Ni electrodes. A final stage of the research focuses on the development of a practical Ag/Ni foam catalyst for the redn. of benzylbromide. Due to the high electrochem. active surface area of Ag/Ni foam, a higher conversion of benzyl bromide was obtained in comparison with bulk Ag.
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    18. 18
      Sui, N.; Wang, K.; Shan, X.; Bai, Q.; Wang, L.; Xiao, H.; Liu, M.; Colvin, V. L.; Yu, W. W. Facile Synthesis of Hollow Dendritic Ag/Pt Alloy Nanoparticles for Enhanced Methanol Oxidation Efficiency. Dalton Trans. 2017, 46, 15541– 15548,  DOI: 10.1039/C7DT03671J
      18
      Facile synthesis of hollow dendritic Ag/Pt alloy nanoparticles for enhanced methanol oxidation efficiency
      Sui, Ning; Wang, Ke; Shan, Xinyao; Bai, Qiang; Wang, Lina; Xiao, Hailian; Liu, Manhong; Colvin, Vicki L.; Yu, William W.
      Dalton Transactions (2017), 46 (44), 15541-15548CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)
      Hollow dendritic Ag/Pt alloy nanoparticles were synthesized by a double template method: Ag nanoparticles as the hard template to obtain hollow spheres by a galvanic replacement reaction between PtCl62- and metallic Ag and surfactant micelles (Brij58) as the soft template to generate porous dendrites. The formation of a Ag/Pt alloy phase was confirmed by XRD and HRTEM. Elemental mapping and line scanning revealed the formation of the hollow architecture. We studied the effects of the Ag/Pt ratio, surfactant and reaction temp. on the morphol. We explored the formation process of hollow dendritic Ag/Pt nanoparticles by tracking the morphologies of the nanostructures formed at different stages. In order to improve the electrocatalytic property, we controlled the size of the nanoparticles and the thickness of the shell by adjusting the amt. of the precursor. We found that these Ag/Pt alloy nanoparticles exhibited high activity (440 mA/mg) and stability as an electrocatalyst for catalyzing MeOH oxidn.
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    19. 19
      Richard-Daniel, J.; Boudreau, D. Enhancing Galvanic Replacement in Plasmonic Hollow Nanoparticles: Understanding the Role of the Speciation of Metal Ion Precursors. ChemNanoMat 2020, 6, 907– 915,  DOI: 10.1002/cnma.202000158
      19
      Enhancing Galvanic Replacement in Plasmonic Hollow Nanoparticles: Understanding the Role of the Speciation of Metal Ion Precursors
      Richard-Daniel, Josee; Boudreau, Denis
      ChemNanoMat (2020), 6 (6), 907-915CODEN: CHEMSB; ISSN:2199-692X. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Hollow nanostructures offer great potential for plasmonic applications due to their strong and highly tunable localized surface plasmon resonance. The relationship between the plasmonic properties and geometry of hollow nanoparticles, such as core-shell size ratio, concentricity of the cavity and porosity of the wall, is well documented. Nanoscale galvanic replacement provides a simple, versatile and powerful route for the prepn. of such hollow structures. Here we demonstrate how the efficiency of reductant-assisted galvanic replacement processes can be enhanced by controlling the degree of hydration and hydrolysis of the metal ion precursor using pH and pL as key control parameters (by analogy to pH, the letter p in the expression pL is used to indicate the decimal cologarithm assocd. with the concn. of the ligand L). Adjusting precursor speciation prior to the sacrificial template's hollowing process offers a new strategy to tune the morphol. and optical properties of plasmonic hollow nanostructures.
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    20. 20
      Wang, M.; Zhang, W.; Wang, J.; Wexler, D.; Poynton, S. D.; Slade, R. C. T.; Liu, H.; Winther-Jensen, B.; Kerr, R.; Shi, D.; Chen, J. PdNi Hollow Nanoparticles for Improved Electrocatalytic Oxygen Reduction in Alkaline Environments. ACS Appl. Mater. Interfaces 2013, 5, 12708– 12715,  DOI: 10.1021/am404090n
      20
      PdNi Hollow Nanoparticles for Improved Electrocatalytic Oxygen Reduction in Alkaline Environments
      Wang, Meng; Zhang, Weimin; Wang, Jiazhao; Wexler, David; Poynton, Simon D.; Slade, Robert C. T.; Liu, Huakun; Winther-Jensen, Bjorn; Kerr, Robert; Shi, Dongqi; Chen, Jun
      ACS Applied Materials & Interfaces (2013), 5 (23), 12708-12715CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
      Pd-Ni hollow nanoparticles were synthesized via a modified galvanic replacement method using Ni nanoparticles as sacrificial templates in an aq. medium. X-ray diffraction and TEM show that the as-synthesized nanoparticles are alloyed nanostructures and have hollow interiors with an av. particle size of 30 nm and shell thickness of 5 nm. Compared with the com. available Pt/C or Pd/C catalysts, the synthesized PdNi/C has superior electrocatalytic performance towards the O redn. reaction, which makes it a promising electrocatalyst for alk. anion exchange membrane fuel cells and alkali-based air-batteries. The electrocatalyst is finally examd. in a H2/O2 alk. anion exchange membrane fuel cell; such electrocatalysts could work in a real fuel cell application as a more efficient catalyst than state-of-the-art com. available Pt/C.
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    21. 21
      Li, C.; Su, Y.; Lv, X.; Shi, H.; Yang, X.; Wang, Y. Enhanced Ethanol Electrooxidation of Hollow Pd Nanospheres Prepared by Galvanic Exchange Reactions. Mater. Lett. 2012, 69, 92– 95,  DOI: 10.1016/j.matlet.2011.11.054
      21
      Enhanced ethanol electrooxidation of hollow Pd nanospheres prepared by galvanic exchange reactions
      Li, Cuiling; Su, Yi; Lv, Xiangyu; Shi, Hongjun; Yang, Xiangguang; Wang, Yujiang
      Materials Letters (2012), 69 (), 92-95CODEN: MLETDJ; ISSN:0167-577X. (Elsevier B.V.)
      In this work hollow Pd nanospheres were successfully synthesized by using galvanic replacement of facile synthesized Cu2O nanospheres with palladium for the first time. The SEM showed the hollow structure of Pd nanospheres and the XRD anal. proved the successful prepn. of Pd. This method is surfactant-free, and well-dispersed hollow Pd nanospheres can be obtained through this route. It was found that the hollow Pd nanospheres showed good electrochem. properties and could be used as catalysts in DEFCs. From cyclic voltammograms, the onset potential of hollow Pd nanospheres shifted neg. by 100 mV and the peak current of hollow Pd nanospheres was about two times higher than that of solid Pd nanospheres.
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    22. 22
      Niu, W.; Li, Z.-Y.; Shi, L.; Liu, X.; Li, H.; Han, S.; Chen, J.; Xu, G. Seed-Mediated Growth of Nearly Monodisperse Palladium Nanocubes with Controllable Sizes. Cryst. Growth Des. 2008, 8, 4440– 4444,  DOI: 10.1021/cg8002433
      22
      Seed-Mediated Growth of Nearly Monodisperse Palladium Nanocubes with Controllable Sizes
      Niu, Wenxin; Li, Zhi-Yuan; Shi, Lihong; Liu, Xiaoqing; Li, Haijuan; Han, Shuang; Chen, Jiuan; Xu, Guobao
      Crystal Growth & Design (2008), 8 (12), 4440-4444CODEN: CGDEFU; ISSN:1528-7483. (American Chemical Society)
      Nearly monodisperse Pd nanocubes with controllable sizes were synthesized through a seed-mediated growth approach. By using Pd nanocubes of 22 nm in size as seeds, the morphol. of the as-grown nanostructures was fixed as single-cryst., which enabled one to rationally tune the size of Pd nanocubes. The formation mechanism of initial 22 nm nanocubes was also discussed. The size-dependent surface plasmon resonance properties of the as-synthesized Pd nanocubes were studied. Compared with previous methods, the yield, monodispersity, perfection of the shape formation, and the range of size control of these nanocubes are all improved. These Pd nanocubes may have potential interests in surface-enhanced Raman scattering, sensors, catalysis, study of size-dependent properties, and fabrication of high-order structures.
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    23. 23
      Wen, X.; Lerch, S.; Wang, Z.; Aboudiab, B.; Tehrani-Bagha, A. R.; Olsson, E.; Moth-Poulsen, K. Synthesis of Palladium Nanodendrites Using a Mixture of Cationic and Anionic Surfactants. Langmuir 2020, 36, 1745– 1753,  DOI: 10.1021/acs.langmuir.9b03804
      23
      Synthesis of Palladium Nanodendrites Using a Mixture of Cationic and Anionic Surfactants
      Wen, Xin; Lerch, Sarah; Wang, Zhihang; Aboudiab, Bassem; Tehrani-Bagha, Ali Reza; Olsson, Eva; Moth-Poulsen, Kasper
      Langmuir (2020), 36 (7), 1745-1753CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)
      Surfactants are used widely to control the synthesis of shaped noble-metal nanoparticles. In this work, a mixt. of hexadecyltrimethylammonium bromide (CTAB), a cationic surfactant; sodium oleate (NaOL), an anionic surfactant; palladium chloride; and a reducing agent were used in the seed-mediated synthesis of palladium nanoparticles. By controlling the surfactant mixt. ratio, we initially discovered that palladium nanodendrites with narrow size distribution were formed instead of the traditional nanocubes, synthesized with only CTAB. In order to investigate the optimal ratio to produce Pd nanodendrites with a high yield and narrow size distribution, samples synthesized with multiple molar ratios of the two surfactants were prepd. and studied by transmission electron microscopy, dynamic light scattering, conductance, and UV-visible spectroscopy. We propose that the addn. of NaOL alters the arrangement of surfactants on the Pd seed surface, leading to a new pattern of growth and aggregation. By studying the nanodendrite growth over time, we identified the redn. period of Pd2+ ions and the formation period of the nanodendrites. Our further expts., including the replacement of CTAB with hexadecyltrimethylammonium chloride (CTAC) and the replacement of NaOL with sodium stearate, showed that CTA+ ions in CTAB and OL- ions in NaOL play the main roles in the formation of nanodendrites. The formation of palladium nanodendrites was robust and achieved with a range of temps., pH and mixing speeds.
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    24. 24
      Niu, W.; Zhang, L.; Xu, G. Shape-Controlled Synthesis of Single-Crystalline Palladium Nanocrystals. ACS Nano 2010, 4, 1987– 1996,  DOI: 10.1021/nn100093y
      24
      Shape-Controlled Synthesis of Single-Crystalline Palladium Nanocrystals
      Niu, Wenxin; Zhang, Ling; Xu, Guobao
      ACS Nano (2010), 4 (4), 1987-1996CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)
      A versatile method for selectively synthesizing single-cryst. rhombic dodecahedral, cubic, and octahedral palladium nanocrystals, as well as their derivs. with varying degrees of edge- and corner-truncation, was reported for the first time. This is also the first report regarding the synthesis of rhombic dodecahedral palladium nanocrystals. All the nanocrystals were readily synthesized by a seed-mediated method with cetyltrimethylammonium bromide as surfactant, KI as additive, and ascorbic acid as reductant. At the same ascorbic acid concn., a series of palladium nanocrystals with varying shapes were obtained through manipulation of the concn. of KI and the reaction temp. The formation of different palladium facets were correlated with their growth conditions. In the absence of KI, the {100} palladium facets are favored. In the presence of KI, the concn. of KI and the reaction temp. play an important role on the formation of different palladium facets. The {110} palladium facets are favored at relatively high temps. and medium KI concns. The {111} palladium facets are favored at relatively low temps. and medium KI concns. The {100} palladium facets are favored at either very low or relatively high KI concns. These correlations were explained in terms of surface-energy and growth kinetics. These results provide a basis for gaining mechanistic insights into the growth of well-faceted metal nanostructures.
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    25. 25
      Lee, C.-L.; Tseng, C.-M.; Wu, R.-B.; Wu, C.-C.; Syu, S.-C. Catalytic characterization of hollow silver/palladium nanoparticles synthesized by a displacement reaction. Electrochim. Acta 2009, 54, 5544– 5547,  DOI: 10.1016/j.electacta.2009.04.056
      25
      Catalytic characterization of hollow silver/palladium nanoparticles synthesized by a displacement reaction
      Lee, Chien-Liang; Tseng, Chun-Ming; Wu, Rong-Bing; Wu, Chen-Chung; Syu, Shu-Ciao
      Electrochimica Acta (2009), 54 (23), 5544-5547CODEN: ELCAAV; ISSN:0013-4686. (Elsevier B.V.)
      Hollow Ag/Pd nanoparticles were successfully prepd. by a galvanic displacement reaction, in which a small amt. of Pd(NO3)2 is allowed to react with previously synthesized Ag nanoparticles that act as templates. The resulting hollow Ag/Pd (Ag/Pdhollow) nanoparticles are icosahedral and decahedral in structure. The kinetics of electroless Cu deposition (ECD) catalyzed by these bimetallic (Ag/Pdhollow) nanoparticles are analyzed using an electrochem. quartz crystal microbalance (EQCM). These Ag/Pdhollow nanoparticles have better catalytic activities than monometallic Ag and Pd nanoparticles. Also, the catalytic activities of these hollow nanoparticles in the ECD bath can be controlled by tuning their alloy ratios in a suitable manner.
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    26. 26
      Chen, D.; Cui, P.; Liu, H.; Yang, J. Catalytic Characterization of Hollow Silver/Palladium Nanoparticles Synthesized by a Displacement Reaction. Electrochim. Acta 2015, 153, 461– 467,  DOI: 10.1016/j.electacta.2014.12.016
      26
      Heterogeneous nanocomposites composed of silver sulfide and hollow structured Pd nanoparticles with enhanced catalytic activity toward formic acid oxidation
      Chen, Dong; Cui, Penglei; Liu, Hui; Yang, Jun
      Electrochimica Acta (2015), 153 (), 461-467CODEN: ELCAAV; ISSN:0013-4686. (Elsevier Ltd.)
      Nanocomposites consisting semiconductor and noble metal domains are of great interest for their synergistic effect-based enhanced properties in a given application. Herein, we demonstrate a facile approach for the synthesis of heterogeneous nanocomposites consisting of silver sulfide (Ag2S) and hollow structured Pd nanoparticles (hPd). It begins with the prepn. of core-shell nanoparticles with an Ag core and an alloy Ag/Pd shell in an org. solvent via galvanic replacement reaction (GRR) between Ag seed particles pre-synthesized and Pd2+ ion precursors. The Ag component is then removed from the core and shell regions of core-shell Ag-Ag/Pd nanoparticles, and converted into Ag2S by elemental sulfur (S). The Ag2S forms the semiconductor domain in the nanocomposite and shares the solid-state interface with the resultant hollow structured Pd nanoparticle. As demonstrated, the Ag2S-hPd nanocomposites exhibit superior catalytic activity and durability for formic acid oxidn., compared to the pure Pd nanoparticles prepd. by oleylamine redn. of Pd ion precursors and com. Pd/C catalyst, due to the electronic coupling between semiconductor and noble metal domains in the nanocomposites. In addn., the structural transformation from core-shell to heterogeneous nanocomposites may provide new opportunities to design and fabricate hybrid nanostructures with interesting physicochem. properties.
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    27. 27
      Ge, J.; Xing, W.; Xue, X.; Liu, C.; Lu, T.; Liao, J. Controllable Synthesis of Pd Nanocatalysts for Direct Formic Acid Fuel Cell (DFAFC) Application: From Pd Hollow Nanospheres to Pd Nanoparticles. J. Phys. Chem. C 2007, 111, 17305– 17310,  DOI: 10.1021/jp073666p
      27
      Controllable Synthesis of Pd Nanocatalysts for Direct Formic Acid Fuel Cell (DFAFC) Application: From Pd Hollow Nanospheres to Pd Nanoparticles
      Ge, Junjie; Xing, Wei; Xue, Xinzhong; Liu, Changpeng; Lu, Tianhong; Liao, Jianhui
      Journal of Physical Chemistry C (2007), 111 (46), 17305-17310CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      The controllable synthesis of nanosized C-supported Pd catalysts through a surface replacement reaction (SRR) is reported. Depending on the synthesis conditions, the Pd can be formed on Co nanoparticle surfaces in hollow nanospheres or nanoparticles structures. The citrate anion acts as a stabilizer for the nanostructures and protonation of the 3rd carboxyl anion - hence the nanostructure and size of the resulting catalysts are controlled by the pH of the synthesis soln. Pd hollow nanospheres, contg. smaller Pd nanoparticles, supported on C, are formed at pH 9. Highly-dispersed C-supported Pd nanoparticles can be formed at pH ≥10. All catalysts prepd. through this SRR method show enhanced activities for the HCOOH electrooxidn. reaction compared to catalysts obtained through NaBH4 redn.
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    28. 28
      Johnson, N. J. J.; Lam, B.; MacLeod, B. P.; Sherbo, R. S.; Moreno-Gonzalez, M.; Fork, D. K.; Berlinguette, C. P. Facets and Vertices Regulate Hydrogen Uptake and Release in Palladium Nanocrystals. Nat. Mater. 2019, 18, 454– 458,  DOI: 10.1038/s41563-019-0308-5
      28
      Facets and vertices regulate hydrogen uptake and release in palladium nanocrystals
      Johnson, Noah J. J.; Lam, Brian; MacLeod, Benjamin P.; Sherbo, Rebecca S.; Moreno-Gonzalez, Marta; Fork, David K.; Berlinguette, Curtis P.
      Nature Materials (2019), 18 (5), 454-458CODEN: NMAACR; ISSN:1476-1122. (Nature Research)
      Crystal facets, vertices and edges govern the energy landscape of metal surfaces and thus the chem. interactions on the surface1,2. The facile absorption and desorption of hydrogen at a palladium surface provides a useful platform for defining how metal-solute interactions impact properties relevant to energy storage, catalysis and sensing3-5. Recent advances in operando and in situ techniques have enabled the phase transitions of single palladium nanocrystals to be temporally and spatially tracked during hydrogen absorption6-11. We demonstrate herein that in situ X-ray diffraction can be used to track both hydrogen absorption and desorption in palladium nanocrystals. This ensemble measurement enabled us to delineate distinctive absorption and desorption mechanisms for nanocrystals contg. exclusively (111) or (100) facets. We show that the rate of hydrogen absorption is higher for those nanocrystals contg. a higher no. of vertices, consistent with hydrogen absorption occurring quickly after β-phase nucleation at lattice-strained vertices9,10. Tracking hydrogen desorption revealed initial desorption rates to be nearly tenfold faster for samples with (100) facets, presumably due to the faster recombination of surface hydrogen atoms. These results inspired us to make nanocrystals with a high no. of vertices and (100) facets, which were found to accommodate fast hydrogen uptake and release.
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    29. 29
      Zhang, Q.; Li, W.; Wen, L.-P.; Chen, J.; Xia, Y. Facile Synthesis of Ag Nanocubes of 30 to 70 nm in Edge Length with CF3COOAg as a Precursor. Chem. – Eur. J. 2010, 16, 10234– 10239,  DOI: 10.1002/chem.201000341
      29
      Facile synthesis of Ag nanocubes of 30 to 70 nm in edge length with CF3COOAg as a precursor
      Zhang, Qiang; Li, Weiyang; Wen, Long-Ping; Chen, Jingyi; Xia, Younan
      Chemistry - A European Journal (2010), 16 (33), 10234-10239, S10234/1-S10234/3CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Ag nanocubes having a 30-70 nm edge length were synthesized by using CF3COOAg as a precursor for elemental silver. By adding a trace amt. of NaSH and HCl in the polyol synthesis, Ag nanocubes were obtained with high quality, high reproducibility, and on a scale of ≤0.19 g per batch for the 70 nm Ag nanocubes. The Ag nanocubes were grew in size at a controllable pace during the synthesis. The linear relationship between the edge length of the Ag nanocubes and position of localized surface plasmon resonance peak provides a simple method for finely tuning and controlling the size of the Ag nanocubes by monitoring the UV/Visible spectra of the reaction at different times.
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    30. 30
      Wang, Y.; Zheng, Y.; Huang, C. Z.; Xia, Y. Synthesis of Ag Nanocubes 18–32 nm in Edge Length: The Effects of Polyol on Reduction Kinetics, Size Control, and Reproducibility. J. Am. Chem. Soc. 2013, 135, 1941– 1951,  DOI: 10.1021/ja311503q
      30
      Synthesis of Ag Nanocubes 18-32 nm in Edge Length: The Effects of Polyol on Reduction Kinetics, Size Control, and Reproducibility
      Wang, Yi; Zheng, Yiqun; Huang, Cheng Zhi; Xia, Younan
      Journal of the American Chemical Society (2013), 135 (5), 1941-1951CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      This article describes a robust method for the facile synthesis of small Ag nanocubes with edge lengths controlled in the range of 18-32 nm. The success of this new method relies on the substitution of ethylene glycol (EG; the solvent most commonly used in a polyol synthesis) with diethylene glycol (DEG). Owing to the increase in hydrocarbon chain length, DEG possesses a higher viscosity and a lower reducing power relative to EG. As a result, we were able to achieve a nucleation burst in the early stage to generate a large no. of seeds and a relatively slow growth rate thereafter; both factors were crit. to the formation of Ag nanocubes with small sizes and in high purity (>95%). The edge length of the Ag nanocubes could be easily tailored in the range of 18-32 nm by quenching the reaction at different time points. For the first time, we were able to produce uniform sub-20 nm Ag nanocubes in a hydrophilic medium and on a scale of ∼20 mg per batch. It is also worth pointing out that the present protocol was remarkably robust, showing good reproducibility between different batches and even for DEGs obtained from different vendors. Our results suggest that the high sensitivity of synthesis outcomes to the trace amts. of impurities in a polyol, a major issue for reproducibility and scale up synthesis, did not exist in the present system.
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    31. 31
      Fu, B.; Liu, W.; Li, Z. Calculation of the Surface Energy of FCC-Metals with the Empirical Electron Surface Model. Appl. Surf. Sci. 2010, 256, 6899– 6907,  DOI: 10.1016/j.apsusc.2010.04.108
      31
      Calculation of the surface energy of fcc-metals with the empirical electron surface model
      Fu, Baoqin; Liu, Wei; Li, Zhilin
      Applied Surface Science (2010), 256 (22), 6899-6907CODEN: ASUSEE; ISSN:0169-4332. (Elsevier B.V.)
      The empirical electron surface model (EESM) based on the empirical electron theory and the dangling bond anal. method has been used to establish a database of surface energy for low-index surfaces of fcc-metals such as Al, Mn, Co, Ni, Cu, Pd, Ag, Pt, Au, and Pb. A brief introduction of EESM will be presented in this paper. The calcd. results are in agreement with exptl. and other theor. values. Comparison of the exptl. results and calcn. values shows that the av. relative error is less than 10% and these values show a strong anisotropy. As we predicted, the surface energy of the close-packed plane (1 1 1) is the lowest one of all index surfaces. For low-index planes, the order of the surface energies is γ(1 1 1) < γ(1 0 0) < γ(1 1 0) < γ(2 1 0). It is also found that the dangling bond electron d. and the spatial distribution of covalent bonds have a great influence on surface energy of various index surfaces.
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    32. 32
      Zhang, J.-M.; Ma, F.; Xu, K.-W. Calculation of the Surface Energy of FCC Metals with Modified Embedded-Atom Method. Chin. Phys. 2004, 13, 1082– 1090,  DOI: 10.1088/1009-1963/13/7/020
      32
      Calculation of the surface energy of fcc metals with modified embedded-atom method
      Zhang, Jian-Min; Ma, Fei; Xu, Ke-wei
      Chinese Physics (Beijing, China) (2004), 13 (7), 1082-1090CODEN: CHPHF4; ISSN:1009-1963. (Chinese Physical Society)
      The surface energies for 38 surfaces of fcc. metals Cu, Ag, Au, Ni, Pd, Pt, Al, Pb, Rh, and Ir were calcd. by the modified embedded-atom method. For Cu, Ag, Ni, Al, Pb, and Ir, the av. values of the surface energies are very close to the polycryst. exptl. data. For all fcc. metals, as predicted, the close-packed (111) surface has the lowest surface energy. The surface energies for the other surfaces increase linearly with increasing angle between the surfaces (hkl) and (111). This can be used to est. the relative values of the surface energy.
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    33. 33
      Huang, Y.; Ferhan, A. R.; Dandapat, A.; Yoon, C. S.; Song, J. E.; Cho, E. C.; Kim, D.-H. A Strategy for the Formation of Gold–Palladium Supra-Nanoparticles from Gold Nanoparticles of Various Shapes and Their Application to High-Performance H2O2 Sensing. J. Phys. Chem. C 2015, 119, 26164– 26170,  DOI: 10.1021/acs.jpcc.5b08423
      33
      A Strategy for the Formation of Gold-Palladium Supra-Nanoparticles from Gold Nanoparticles of Various Shapes and Their Application to High-Performance H2O2 Sensing
      Huang, Youju; Ferhan, Abdul Rahim; Dandapat, Anirban; Yoon, Chong Seung; Song, Ji Eun; Cho, Eun Chul; Kim, Dong-Hwan
      Journal of Physical Chemistry C (2015), 119 (46), 26164-26170CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      The authors present a new approach for the synthesis of gold (Au)-palladium (Pd) bimetallic supra-nanoparticles in which densely packed anisotropic Pd nanostructures surround a central Au nanoparticle (rod, sphere, cubic shape). They were obtained by Pd crystal growth on Au nanoparticle surfaces which are modified with a mixt. of cetyltrimethylammonium bromide (CTAB) and 5-bromosalicylic acid (5-BrSA). From a comparative study with a Au nanorod (NR) as a seed, the use of the CTAB/5-BrSA mixt. plays a pivotal role in obtaining such unique supra-structures; the Au NR capped with only CTAB resulted in Au core-continuous Pd shell nanoparticles instead. The Au-Pd supra-nanoparticles provide active surface area for electrocatalytic activities higher than that of the Au@Pd continuous shell nanoparticles, displaying outstanding performance for mediator-free electrochem. detection of H2O2.
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    34. 34
      Pekkari, A.; Wen, X.; Orrego, J. R.; Silva, R. R.; Kondo, S.; Olsson, E.; Härelind, H.; Moth-Poulsen, K. Synthesis of Highly Monodisperse Pd Nanoparticles Using a Binary Surfactant Combination and Sodium Oleate as a Reductant. Nanoscale Adv. 2021, 3, 2481– 2487,  DOI: 10.1039/D1NA00052G
      34
      Synthesis of highly monodisperse Pd nanoparticles using a binary surfactant combination and sodium oleate as a reductant
      Pekkari, Anna; Wen, Xin; Orrego-Hernandez, Jessica; da Silva, Robson Rosa; Kondo, Shun; Olsson, Eva; Haerelind, Hanna; Moth-Poulsen, Kasper
      Nanoscale Advances (2021), 3 (9), 2481-2487CODEN: NAADAI; ISSN:2516-0230. (Royal Society of Chemistry)
      This study presents the synthesis of monodisperse Pd nanoparticles (NPs) stabilized by sodium oleate (NaOL) and hexadecyltrimethylammonium chloride (CTAC). The synthesis was conducted without traditional reductants and Pd-precursors are reduced by NaOL. It was confirmed that the alkyl double bond in NaOL is not the only explanation for the redn. of Pd-precursors since Pd NPs could be synthesized with CTAC and the satd. fatty acid sodium stearate (NaST). A quant. evaluation of the redn. kinetics using UV-Vis spectroscopy shows that Pd NPs synthesized with both stabilizer combinations follow pseudo first-order reaction kinetics, where NaOL provides a faster and more effective redn. of Pd-precursors. The colloidal stabilization of the NP surface by CTAC and NaOL is confirmed by Fourier transform IR (FTIR) and NMR (NMR) anal.
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  • Supporting Information

    Supporting Information

    The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.langmuir.3c00799.

    • TEM images of hollow Ag–Pd nanodendrites and nanoboxes at different growth times; histograms of the size distribution of Ag nanocubes, hollow Ag–Pd nanodendrites, and nanoboxes; atomic percent of Ag and Pd in hollow Ag–Pd nanodendrites and nanoboxes detected by energy-dispersive X-ray spectroscopy from four regions and their average percent; extinction spectra and TEM images of hollow Ag–Pd nanodendrites synthesized by adding 5, 25, and 100 μL of Ag seed suspension, respectively; histograms of the size distribution of the hollow Ag–Pd nanodendrites; TEM images of hollow Ag–Pd nanodendrites synthesized by using palladium(II) acetate and sodium tetrachloropalladate as Pd precursors; TEM images of Ag–Pd particles prepared using the standard procedure except that no CTAC was replaced by the same molar concentration of KF, KCl, KBr, and KI (PDF)


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