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Theoretical Approach To Predict the Stability of Supported Single-Atom Catalysts
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  • Ya-Qiong Su
    Ya-Qiong Su
    Laboratory of Inorganic Materials & Catalysis, Schuit Institute of Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
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    Orcidhttp://orcid.org/0000-0001-5581-5352
  • Yifan Wang
    Yifan Wang
    Department of Chemical and Biomolecular Engineering, Catalysis Center for Energy Innovation, University of Delaware, 221 Academy Street, Newark, Delaware 19716, United States
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  • Jin-Xun Liu
    Jin-Xun Liu
    Laboratory of Inorganic Materials & Catalysis, Schuit Institute of Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
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    Orcidhttp://orcid.org/0000-0002-7499-4197
  • Ivo A.W. Filot
    Ivo A.W. Filot
    Laboratory of Inorganic Materials & Catalysis, Schuit Institute of Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
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  • Konstantinos Alexopoulos
    Konstantinos Alexopoulos
    Department of Chemical and Biomolecular Engineering, Catalysis Center for Energy Innovation, University of Delaware, 221 Academy Street, Newark, Delaware 19716, United States
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  • Long Zhang
    Long Zhang
    Laboratory of Inorganic Materials & Catalysis, Schuit Institute of Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
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  • Valerii Muravev
    Valerii Muravev
    Laboratory of Inorganic Materials & Catalysis, Schuit Institute of Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
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  • Bart Zijlstra
    Bart Zijlstra
    Laboratory of Inorganic Materials & Catalysis, Schuit Institute of Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
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    Orcidhttp://orcid.org/0000-0002-4040-6545
  • Dionisios G. Vlachos*
    Dionisios G. Vlachos
    Department of Chemical and Biomolecular Engineering, Catalysis Center for Energy Innovation, University of Delaware, 221 Academy Street, Newark, Delaware 19716, United States
    *E-mail: [email protected]
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    Orcidhttp://orcid.org/0000-0002-6795-8403
  • Emiel J.M. Hensen*
    Emiel J.M. Hensen
    Laboratory of Inorganic Materials & Catalysis, Schuit Institute of Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
    *E-mail: [email protected]
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    Orcidhttp://orcid.org/0000-0002-9754-2417
Open PDFSupporting Information (1)

ACS Catalysis

Cite this: ACS Catal. 2019, 9, 4, 3289–3297
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https://doi.org/10.1021/acscatal.9b00252
Published March 5, 2019

Copyright © 2019 American Chemical Society. This publication is licensed under CC-BY-NC-ND.

Abstract

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Heterogeneous single-atom catalysts involve isolated metal atoms anchored to a support, displaying high catalytic performance and stability in many important chemical reactions. We present a general theoretical framework to establish the thermodynamic stability of metal single atoms and metal nanoparticles on a support in the presence of adsorbates. As a case study, we establish for Pt–CeO2 the CO partial pressure and temperature range within which Pt single atoms are more stable than Pt nanoparticles. Density functional theory and kinetic Monte Carlo simulations demonstrate that Pt atoms doped into the CeO2 surface exhibit a very high CO oxidation activity and thermodynamic stability in comparison to models involving Pt single atoms on terraces and steps of CeO2. An intermediate CO adsorption strength is important to explain a high activity. Our work provides a systematic strategy to evaluate the stability and reactivity of single atoms on a support.

Copyright © 2019 American Chemical Society

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Introduction

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Supported metal catalysts are extensively used in exhaust gas cleanup because of their high catalytic activity for CO and hydrocarbon oxidation and NOx reduction. (1−3) The size of the supported metal nanoparticles (NPs) is often decisive for the catalytic performance. (4−6) Due to their highly undercoordinated nature, supported metal single-atom catalysts (SACs) can display a very high catalytic activity. SACs are rapidly becoming a new frontier in heterogeneous catalysis. (7−9) Besides the low coordination number of the catalytic metal atom, the support usually plays an important role in the catalytic cycle, akin to noninnocent ligands in homogeneous catalysts. (10,11)
In environmental catalysis, ceria is one of the most used supports, because it can reversibly store oxygen atoms and also because it strongly interacts with transition metals, leading to a large metal–support interface. (12,13) Generally, single atoms (SAs) are more mobile on a support than NPs and, thus, prone to agglomeration. (14−16) SA stabilization on oxide supports is therefore of critical importance for the design of SACs. The preparation and performance of Pt SAs on ceria have recently been extensively studied. (1,8,17−19) Experimental and theoretical data also emphasize the role of surface defects in ceria, such as steps and cation vacancies, for trapping of Pt SAs. (1,8,18) Alternatively, Pt SAs can also strongly interact with the less stable CeO2(100) surface by coordinating to four surface oxygen atoms in a square-planar configuration. (8,19) Another aspect of highly dispersed supported metal systems is the strong adsorption of reactants that can lead to the breakup and dispersion of metal clusters and nanoparticles into SAs. (20−25) For instance, Berko et al. observed by scanning tunneling microscopy a very rapid disintegration of TiO2-supported Rh NPs of 1–2 nm to atomically dispersed Rh at 300 K and a pressure of 10–1 mbar CO. (22)
On the basis of binding energies computed by density functional theory (DFT), we develop a theoretical framework that forms the basis for constructing condition-dependent stability diagrams of supported metal SAs with respect to supported metal NPs in the presence of CO. The influence of CO coverage and lateral interactions is also taken into account. This leads to predictions about the stability of NPs and a critical size below which the supported NPs will disperse into SAs in the presence of CO at given conditions. We employ this methodology to predict the stability of Pt SAs on stoichiometric CeO2(111), stepped CeO2(111), defective CeO2(111), and CeO2(100) surfaces. Finally, we compute potential energy diagrams for CO oxidation by Pt SAs for several of these cases. CO oxidation rates are predicted by graph-theoretical kinetic Monte Carlo (GT-kMC) simulations. (26)

Computational Methods

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Density Functional Theory (DFT)

We carried out spin-polarized DFT calculations as implemented in the Vienna ab initio simulation package (VASP). (27) The ion–electron interactions are represented by the projector-augmented wave (PAW) method (28) and the electron exchange-correlation by the generalized gradient approximation (GGA) with the Perdew–Burke–Ernzerhof (PBE) exchange-correlation functional. (29) The Kohn–Sham valence states were expanded in a plane-wave basis set with a cutoff energy of 400 eV. The Ce(5s,5p,6s,4f,5d), O(2s,2p), Pd(4d5s), and C(2s,2p) electrons were treated as valence states. The DFT+U approach was used, in which U is a Hubbard-like term describing the on-site Coulombic interactions. (30) This approach improves the description of localized states in ceria, where standard LDA and GGA functionals fail. For Ce, a value of U = 4.5 eV was adopted, which was calculated self-consistently by Fabris et al. (31) using the linear response approach of Cococcioni and de Gironcoli (32) and is within the 3.0–6.0 eV range that results in the localization in Ce 4f orbitals of the electrons left upon oxygen removal from ceria. (33)
For Pt/CeO2(111), we use a periodic ceria slab with a (4 × 4) surface unit cell. For Brillouin zone integration, a 1 × 1 × 1 Monkhorst–Pack mesh was used. The bulk equilibrium lattice constant (5.49 Å) previously calculated at the PBE+U level (U = 4.5 eV) was used. (34) The CeO2(111) slab model consists of three Ce–O–Ce layers (48 Ce and 96 O atoms) and a vacuum gap of 15 Å. The atoms in the bottom layer were frozen to their bulk positions, and only the top two Ce–O–Ce layers were relaxed. The climbing image nudged-elastic band (CI-NEB) algorithm (35,36) was used to identify the transition states in the elementary reaction steps of CO oxidation. A frequency analysis was performed to confirm that each transition state has only a single imaginary frequency in the direction of the reaction coordinate. The total energy difference was less than 10–4 eV, and the relaxation convergence criterion was set at 0.05 eV/Å.

Graph-Theoretical Kinetic Monte Carlo (GT-kMC)

The DFT-calculated energetics and vibrational frequencies were input in the GT-kMC framework as implemented in the software package Zacros. (37) In this approach, participating species and elementary steps are represented as graphs.
For nonactivated adsorption as employed in this work, we assume an early 2D gas-like transition state. The rate constants of adsorption and desorption are calculated as (26,38,39)
(1)
(2)
here h is Planck’s constant, kB is Boltzmann’s constant, T is the temperature, Px is the partial pressure of a species x, Ast is the area of an adsorption site, m is the molecular mass of the adsorbent, is the gas adsorption energy, and q is the partition function for gas-phase species and adsorbates (computed using statistical mechanical expressions). For each surface reaction, the rate constants were calculated by transition state theory in an Arrhenius form, (40) yielding
(3)
and
(4)
where kfwd (krev) is the rate constant of the forward (reverse) elementary reaction step, kB is the Boltzmann constant, T is the temperature, and h is Planck’s constant. Q‡, QR, and QP are the quasi-partition functions of the transition, reactant, and product states, respectively. Finally, () is the activation energy for configuration σ in the forward (backward) direction. Other inputs to the software include the operating conditions (temperature, pressure, and gas-phase composition), a lattice structure, energetics of each surface species, and the reaction mechanism parametrized by eqs 1–4. (26,41) We did not take into account lateral interactions, because we only consider dispersed single Pt atoms and their neighboring sites, as such interactions between adsorbates are irrelevant. The GT-kMC supports site-dependent chemistry. Three types of sites were considered in each unit cell including a Pt atom, to which CO can adsorb, and two oxygen vacancy sites, where O2 can adsorb and dissociate (see Supporting Information).
The chemical master equation describes the time evolution of the probability pi(t) of finding the system in a particular state i (42)
(5)
where denotes the propensity of the system going from state i to j, which is related to the rate constants of the microscopic events. (43,44) Solving the chemical master equation numerically is often impractical due to the large number of possible states. Instead, the kMC framework solves the chemical master equation stochastically. At each instant, the possible next events on the lattice are identified by solving subgraph isomorphism problems given the current lattice configurations. The probability of a queue of events is generated, and one event is chosen proportional to its probability (26)
(6)
where t is the current time and τi is the time increment between the current time t and the next event i. The time increment is generated stochastically for all possible events at time t following an exponential distribution
(7)
here u is a random number sampled from the uniform distribution between 0 and 1. These times are stored in a priority queue in the form of a binary heap structure. The event i with the smallest occurrence time occurs next. Next, the lattice and simulation time are updated. The procedure is repeated until the stopping criteria are reached. In practice, to reduce stochastic noise, multiple independent trajectories generated using different random seeds are run in parallel and averaged. Given a long enough simulation time, steady-state properties such as average surface species coverages, turnover frequency (TOF), and reaction orders can be obtained.

Results and Discussion

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Stability of Supported NPs and SAs

The driving force for sintering of supported metal catalysts is the reduction in surface free energy of the active metal phase. Metals usually cannot be kept in atomic dispersion on a support, because a metal adatom usually does not bind strong enough to the support. (14) The cohesive energy is typically used to account for the strength of metallic bonds in NPs. Its absolute value decreases when particles become smaller, indicative of the weaker metallic bonds in NPs compared to bulk metal. When a nanoparticle is placed on a support, the total energy is lowered by the interactions with a part of the metal atoms that form the interface. However, the influence of the support on the total energy is minor for particles with more than 20 atoms, and we can use the cohesive energy of the corresponding free NP in vacuum as a first approximation as demonstrated for Pd NPs on CeO2(111). (14) In order to compare stabilities, this cohesive (or binding) energy per metal atom for the supported NP system can be compared to the binding energy of a single metal adatom placed on a support. We develop our approach for Pt on the most stable CeO2(111) surface. The resulting expressions for the binding energies of ceria-supported Pt NPs and a ceria-supported single Pt atom, Pt1/CeO2(111), are
(8)
and
(9)
where , , , andare the energies of a free single Pt atom, a free Pt NP, the CeO2(111) slab, and the Pt1/CeO2(111) model, respectively, and n is the number of Pt atoms in a NP. The binding energy for a free metal NP of n atoms scales with n–1/3 (Figure S1). (45,46) We compute a binding energy of 3.21 eV for a single Pt atom on the most stable CeO2(111) termination, which is close to the earlier reported value of 3.30 eV. (8)
Adsorbates like CO stabilize a supported single Pt adatom more than a Pt NP because of the stronger adsorption of CO to a single metal atom and also because only a fraction of the Pt atoms in a NP is covered by CO, shown in Figure 1. The binding energy of a single Pt atom with adsorbed CO as a function of temperature (T) and pressure (P) is given by
(10)
in which μ is the chemical potential of CO in the gas phase at temperature T and a CO partial pressure P with respect to a reference state of CO in the gas phase at standard conditions. Here, we ignored the contribution of vibrational entropy of the adsorbed CO to the binding energy of a single Pt atom or Pt NPs. The vibrational entropy contribution to the free energy is less than 0.03 eV for CO adsorption on the metal surface. (47−50) The computed adsorption energy of CO on Pt1/CeO2(111), , is −3.45 eV. Accordingly, we can rewrite eq 10 as
(11)

Figure 1

Figure 1. Schematic illustration of the relative stability of Pt SAs and NPs on CeO2 in the presence of adsorbed CO molecules.

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CO adsorption also stabilizes a supported Pt NP. The stabilization will depend on the number of available surface Pt atoms and the CO coverage at a certain T and P. Therefore, we evaluate the binding energy per Pt atom for such a system by taking into account that m CO adsorbs to a NP containing n Pt atoms at a given temperature and pressure
(12)
here, is the average CO adsorption energy obtained from the DFT-computed data
(13)
Thus, the binding energy of a CO-covered Pt NP can be expressed in terms of the binding energy of the free Pt NP and a correction for the adsorption of CO. This correction term can be computed in the following manner by taking the chemical potential of CO molecules into account
(14)
where ω(n) = N/n, i.e., the ratio between the number of surface Pt sites to which CO can adsorb (N) and the total number of Pt atoms (n) and θ = m/N, i.e., the surface coverage at given temperature and pressure.
As we will show below, ω(n) depends strongly on the particle size
(15)
in which is the binding energy of Pt bulk (6.40 eV) extrapolated from Figure S1, is the surface energy of Pt NPs, and Aatom = A/N is the area of a surface atom of Pt. The detailed derivation of eq 15 is in the Supporting Information. To compute the surface energy of Pt NPs, we use the Wulff construction to estimate that sufficiently large NPs consist of 65% (111) and 35% (100) facets. The explicitly calculated binding energy of Pt bulk is 6.37 eV, in accordance with the extrapolated value of 6.40 eV. Accordingly, we neglect the more reactive atoms at the edges and corners. The surface free energy is then the weighted surface energy based on DFT-computed values.
Equation 15 can be generally used for the prediction of the dispersion of free metal NPs. For the supported NPs considered in our study, we assume that one of the surface facets of the cuboctahedra NPs (predicted by the Wulff theorem) forms an interface with the CeO2(111) support. In this way, we can determine ω(n) as a function of n for the nonwetting case. The deviation between ω(n) for free and supported NPs is relatively small. We also considered the case of partial wetting in which one-half of the Wulff shape is visible in a Winterbottom approach. (51) This partial wetting case results in a lower ω(n) for given n (Figure S3). Nevertheless, ω(n) depends much less on the wetting degree than on n.
On the basis of these assumptions for the surface energy and ω(n) we can write the correction term as
(16)
in which f1 and f2 are the fractions of the NP surface occupied by (111) and (100) facets. The binding energy per Pt atom for our Ptn/CeO2(111) system at a given temperature and pressure is then given by
(17)
The coverage dependence of the CO adsorption energy for the Pt(111) and Pt(100) surface facets was evaluated by DFT calculations of CO adsorption in a (3 × 3) surface unit cell and fitted with polynomial functions (Figure 2a). At a given T and P, the corresponding coverage of CO can be determined by (21)
(18)
where is the differential adsorption energy of CO molecules on a particular facet (here, either the (111) or the (100) facet). As an example, Figure 2b shows the CO coverage on Pt(111) facets as a function of T and P. These predictions compare well with available experimental data for single-crystal Pt(111) data. (52−54)

Figure 2

Figure 2. (a) Computed CO adsorption energy on Pt(111) and Pt(100) facets as a function of the CO coverage and (b) CO coverage at given temperature and CO partial pressure for Pt(111).

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We can now determine n, T, and P for which a Pt NP with n Pt atoms covered with m CO is equally or less stable than a CO-covered single Pt atom located on CeO2(111)
(19)
We depict the results in Figure 3a in which the isolines represent this condition for a given n. Figure 3a predicts that, at a typical condition of low-temperature CO oxidation (PCO = 10–5 atm, T = 100 °C), Pt(CO) can be dislodged from Pt NPs of up to ∼150 atoms on the CeO2(111) terrace. Particles larger than this critical size will not break up to form Pt SAs. With increasing CO partial pressure, Pt SAs can compete with larger Pt NP. The reason is that the higher coverage of CO on the Pt NPs means that the larger number of Pt–CO bonds can increasingly outweigh the Pt–Pt interactions in the Pt NP. If, on the other hand, the temperature is raised, the CO coverage will decrease and Pt NP will become increasingly favored over single Pt(CO) species (e.g., T > 300 °C). It can explain some experimental observations that CO induces sintering of metal adatoms on oxide supports at extremely low CO pressure and/or high temperature. (55)Figure 3b and Figure S4 show how these predictions are affected by the wetting of the CeO2(111) surface by the Pt NPs. Clearly, the main trends remain very similar, while increasing wetting leads to a lower dispersion and a lower stability of Pt NPs.

Figure 3

Figure 3. Critical size diagrams of the supported Pt NPs with respect to the thermodynamic stability as a function of temperature and CO partial pressure relative to isolated Pt SAs (a) on the terrace of CeO2(111) with nonwetting and (b) wetting, (c) on the step-edges of CeO2(111), and (d) on the terrace of CeO2(100). Gray area relates to Pt NPs with less than 38 atoms, which were not considered in this study.

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It is important to emphasize that these predictions refer to the thermodynamic stability of an isolated Pt–carbonyl species in comparison to CO-covered Pt NPs. In experiment, the size of the NPs is determined by many factors including the preparation and activation (reduction) method. (56) The dislodgement of a Pt–carbonyl species from a supported Pt NP will involve overcoming a kinetic barrier. For instance, the activation barrier for dislodging a Pt atom from CeO2-supported Pt4 is 2.46 eV. This barrier decreases to 0.45 eV when a CO is adsorbed to the dislodging Pt atom. When the Pt4 cluster is covered by 4 CO, the cluster will spontaneously break up into 4 Pt(CO) SA species (Figure S5). The activation barrier for dislodging a Pt atom from a Pt8 cluster amounts to 2.14 and 0.61 eV in the absence and presence of CO, respectively (Figure S6). Therefore, these results demonstrate that dislodgement of Pt atoms in the presence of CO is feasible at typical reaction conditions.
The computed frequency of the CO stretching vibration for the Pt(CO) SA on CeO2(111) is 2047 cm–1. Notably, this value is significantly different from the typical frequencies of linearly adsorbed CO on Pt(111) and Pt(100), which are 2090 and 2080 cm–1, respectively. (57−60) Bazin et al. observed a CO feature at 2046 cm–1 and attributed this to linear CO adsorption on a Pt atom at the Pt–CeO2 interface in Pt/CeO2. (61) Teschner and co-workers also reported that linear CO adsorption leads to the strongest adsorption at the Pt–CeO2 boundary and a vibrational frequency of 2054 cm–1. (62) Therefore, we speculate that these signals should be attributed to dislodged Pt(CO). We also refer to related IR studies of CO adsorption on oxide-supported Pt catalysts. (63,64)
The binding energy of a Pt atom at the ceria step edge is much higher (5.54 eV) than that on CeO2(111) (3.21 eV). This leads to a higher propensity of ceria step-edge sites to break up Pt NP, as shown in Figure 3c. These results show that atomically dispersed Pt can be stabilized on a ceria step edge over a much wider range of conditions than on the CeO2(111) surface. (18) The finding that this stability extends to high temperature and low CO coverage can explain why ceria-supported small Pt NPs are atomically dispersed at high temperatures, where kinetic barriers for atom dislodgement from Pt NPs can be easily overcome. (1,18) On the basis of the similar stability of Pt(CO) complexes on the CeO2(111) step and CeO2(100), we predict that Pt SAs can also be stabilized over a wide range of conditions on the more open CeO2(100) surface (Figure 3d), in agreement with experimental observations. (65)
Pd doping in the CeO2(111) surface has recently been explored in the context of stable CO and CH4 oxidation catalysis. (66)Figure 4c–f shows similar structures for a Pt atom doped in the CeO2(111) surface. Pt-dop-I contains an octahedral Pt atom obtained by placing a Pt atom on a Ce vacancy (ΔE = −4.04 eV with respect to bulk Pt). (67) Pt-dop-II represents a slightly less stable structure (ΔE = +0.36 eV) in which Pt is located in a square-planar coordination between 4 lattice oxygens. Whereas removal of a surface oxygen from Pt-dop-I is endothermic (ΔE = 1.75 eV), forming an O vacancy (VO) on Pt-dop-II is exothermic (Pt-dop-II-VO, ΔE = −0.35 eV). Removing a further oxygen from Pt-dop-II-VO is unfavorable (ΔE = 1.23 eV), however. Notably, Figure 4d–f shows that the local geometry around Pt in Pt-dop-II is very similar to that of a Pt atom at a step edge to which two excess O atoms are bound (Figure 4b). (8) A phase diagram of these doped structures depicted in Figure 4g predicts that, under typical CO oxidation conditions, Pt-dop–II-VO is a thermodynamically stable structure.

Figure 4

Figure 4. Pt SAs located at a CeO2(111) step before (a) and after (b) O2 dissociation, and (c–f) doped into the CeO2(111) surface (color code: white, Ce; gray, irrelevant O; red, relevant O; black, C; blue, Pt). (g) Ab initio-determined phase diagram of the Pt-doped CeO2(111) surface.

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CO Oxidation

Having established the conditions under which isolated Pt1(CO) complexes are stable on the CeO2(111) terrace and step edges, we will now compare the rate of CO oxidation on different isolated Pt species. We also explored alternative locations of a Pt SA doped into the CeO2(111) surface. Co-adsorption of O2 on isolated Pt(CO) is unfavorable (Eads = 0.08 eV). This implies that CO oxidation via a conventional Langmuir–Hinshelwood (LH) mechanism is unlikely. Therefore, we explored a Mars–van Krevelen (MvK) mechanism involving lattice O atoms of the ceria support. (1,17,68)Figure 5 shows the potential energy surface for CO oxidation. It is shown that the rate-limiting step on Pt1/CeO2(111) and Pt1O2/step is CO2 desorption, which costs energy of 2.38 and 1.31 eV to produce an oxygen vacancy, respectively, while for CO oxidation by Pt-dop-II-VO, the CO2 desorption is much easier and requires an energy barrier of 0.97 eV for CO2 formation. Notably, CO adsorption can cause dynamic hopping of Pt dopants from subsurface to surface as well as Pd. (66)

Figure 5

Figure 5. CO oxidation pathways by Pt SAs on CeO2(111), on stepped CeO2(111), and doped in the CeO2(111) surface.

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Next, we employed the GT-kMC simulations to determine the catalytic performance of these candidate sites in CO oxidation. The lattice for these kinetic Monte Carlo simulations consists of 100 Pt SA on ceria lattice consisting of 10 × 10 unit cells. Each cell contains 1 Pt atom and 2 empty sites accommodating O atoms. The steady-state turnover frequencies (TOF) and occupation of the states along the potential energy surface expressed in terms of fractional coverages are reported in Figure 6. The total pressure is set to 0.1 atm and the CO-to-O2 ratio to 2.

Figure 6

Figure 6. (a) Arrhenius plot of the rate of CO oxidation on three types of Pt SA on ceria. (b–d) Steady-state coverages of dominant surface states of Pt SAs on CeO2(111) during CO oxidation (p = 0.1 atm, CO/O2 ratio = 2).

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Figure 6a shows the CO oxidation rates of the different Pt SAs supported on ceria as a function of the temperature. The Pt-dop-II-VO site is much more reactive than the Pt1O2/step model, while the Pt1/CeO2(111) is nearly inactive for CO oxidation under practical conditions. Recently, Datye and co-workers also suggested that atomically dispersed Pt on step edges of CeO2 exhibits low low-temperature CO oxidation activity. (18) Our study alternatively suggests that Pt atoms doped into the surface can be very active for CO oxidation.
Further insight can be obtained by inspecting the dominant surface states (also known as MARI, most abundant reaction intermediate) during CO oxidation in Figure 6b–d. For Pt1O2/step, the dominant state is CO adsorbed on Pt1O/step at all temperatures tested, indicating strong CO adsorption. In the Pt1/CeO2(111) model, strong CO adsorption results in the CO-adsorbed state on Pt1O/CeO2(111) being the MARI at high temperatures and adsorbed CO2 at low temperatures. On Pt-dop-II-VO, at high temperatures (T > 600 K), the system is in the initial state Int0 (Pt-dop-II-VO), where CO oxidation becomes rate limiting. Reaction orders were also computed and emphasize that CO reaction orders are zero when the MARI is a CO-adsorbed state and unity for an empty surface (Figure S16). This discussion is further supported by a degree of rate control analysis (Figure S18). Overall, we find that strong CO adsorption leads to higher barriers for CO oxidation. Moderate CO bonding of a Pt atom embedded in the CeO2(111) surface is therefore preferred to achieve high CO oxidation activity.

Conclusion

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We developed a novel methodology to determine the thermodynamic stability difference between supported metal SAs and NPs in the presence of adsorbates at a given pressure and temperature. As an example, we investigated under which conditions Pt(CO) complexes may be more stable than (partially) CO-covered Pt NPs on CeO2 surface. The constructed stability diagrams show that isolated Pt(CO) may be expected to form on the terrace and step and doping sites of CeO2(111). In general, the thermodynamic propensity for dislodgement increases with lower temperature and higher CO coverage. Kinetically, CO coverage facilitates the disruption of Pt–Pt bonds. Further investigation of CO oxidation reactivity demonstrates that doping of Pt in the CeO2(111) surface presents the highest CO oxidation turnover rate among the SA models. This is mainly because CO strongly binds to a Pt SA located on the stoichiometric CeO2 surface or Pt1O on a ceria step-edge site, resulting in low activity. The moderate CO binding suggests the importance of a Sabatier optimum for CO oxidation for Pt SAs on CeO2. The herein developed single-atom thermodynamic concept can be generally applied for supported metal catalysts. This study provides deeper insight into the stability and activity of SACs and establishes a useful concept facilitating the rational design of SACs with high stability and catalytic activity.

Supporting Information

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The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acscatal.9b00252.

  • Derivation of the dispersion formula; critical size diagrams of supported Pt NPs and frequency analyses of CO bound to Pt facets; kinetic data of Pt atom dislodging from Pt4 and Pt8 supported on CeO2(111); DFT-determined catalytic cycles of CO oxidation and GT-kMC data (PDF)

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Author Information

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  • Corresponding Authors
  • Authors
    • Ya-Qiong Su - Laboratory of Inorganic Materials & Catalysis, Schuit Institute of Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands;  Orcidhttp://orcid.org/0000-0001-5581-5352
    • Yifan Wang - Department of Chemical and Biomolecular Engineering, Catalysis Center for Energy Innovation, University of Delaware, 221 Academy Street, Newark, Delaware 19716, United States
    • Jin-Xun Liu - Laboratory of Inorganic Materials & Catalysis, Schuit Institute of Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands;  Orcidhttp://orcid.org/0000-0002-7499-4197
    • Ivo A.W. Filot - Laboratory of Inorganic Materials & Catalysis, Schuit Institute of Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
    • Konstantinos Alexopoulos - Department of Chemical and Biomolecular Engineering, Catalysis Center for Energy Innovation, University of Delaware, 221 Academy Street, Newark, Delaware 19716, United States
    • Long Zhang - Laboratory of Inorganic Materials & Catalysis, Schuit Institute of Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
    • Valerii Muravev - Laboratory of Inorganic Materials & Catalysis, Schuit Institute of Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
    • Bart Zijlstra - Laboratory of Inorganic Materials & Catalysis, Schuit Institute of Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands;  Orcidhttp://orcid.org/0000-0002-4040-6545
  • Author Contributions

    Y.S., Y.W., and J.L.: These authors contributed equally.

  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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The authors acknowledge financial support for the research from The Netherlands Organization for Scientific Research (NWO) through a Vici grant and Nuffic funding. Supercomputing facilities were provided by NWO. This work has received funding from the European Union’s Horizon 2020 research and innovation programme under grant no. 686086 (Partial-PGMs). K.A., Y.W., and D.G.V. acknowledge support for the GT-KMC studies from the Catalysis Center for Energy Innovation, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award No. DE-SC0001004. Y.W. acknowledges also support from the Ferguson fellowship.

References

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This article references 68 other publications.

  1. 1
    Nie, L.; Mei, D.; Xiong, H.; Peng, B.; Ren, Z.; Hernandez, X. I. P.; DeLaRiva, A.; Wang, M.; Engelhard, M. H.; Kovarik, L. Activation of Surface Lattice Oxygen in Single-Atom Pt/CeO2 for Low-Temperature CO Oxidation. Science 2017, 358, 1419– 1423,  DOI: 10.1126/science.aao2109
    Google Scholar
    1
    Activation of surface lattice oxygen in single-atom Pt/CeO2 for low temperature CO oxidation
    Nie, Lei; Mei, Donghai; Xiong, Haifeng; Peng, Bo; Ren, Zhibo; Hernandez, Xavier Isidro Pereira; De La Riva, Andrew; Wang, Meng; Engelhard, Mark H.; Kovarik, Libor; Datye, Abhaya K.; Wang, Yong
    Science (Washington, DC, United States) (2017), 358 (6369), 1419-1423CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
    To improve fuel efficiency, advanced combustion engines are being designed to minimize the amt. of heat wasted in the exhaust. Hence, future generations of catalysts must perform at temps. that are 100° lower than current exhaust-treatment catalysts. Achieving low-temp. activity, while surviving the harsh conditions encountered at high engine loads, remains a formidable challenge. Atomically dispersed ionic Pt (Pt2+) on ceria (CeO2), which is already thermally stable, can be activated via steam treatment (at 750°) to simultaneously achieve the goals of low-temp. CO oxidn. activity while providing outstanding hydrothermal stability. A new type of active site is created on CeO2 in the vicinity of Pt2+, which provides the improved reactivity. These active sites are stable up to 800° in oxidizing environments.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhvFGmtr%252FM&md5=2aa1525b0c0fe9271ce995d7e2f8d454
  2. 2
    Qiao, B.; Wang, A.; Yang, X.; Allard, L. F.; Jiang, Z.; Cui, Y.; Liu, J.; Li, J.; Zhang, T. Single-Atom Catalysis of CO Oxidation Using Pt1/FeOx. Nat. Chem. 2011, 3, 634– 641,  DOI: 10.1038/nchem.1095
    Google Scholar
    2
    Single-atom catalysis of CO oxidation using Pt1/FeOx
    Qiao, Botao; Wang, Aiqin; Yang, Xiaofeng; Allard, Lawrence F.; Jiang, Zheng; Cui, Yitao; Liu, Jingyue; Li, Jun; Zhang, Tao
    Nature Chemistry (2011), 3 (8), 634-641CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)
    Platinum-based heterogeneous catalysts are crit. to many important com. chem. processes, but their efficiency is extremely low on a per metal atom basis, because only the surface active-site atoms are used. Catalysts with single-atom dispersions are thus highly desirable to maximize atom efficiency, but making them is challenging. Here we report the synthesis of a single-atom catalyst that consists of only isolated single Pt atoms anchored to the surfaces of iron oxide nanocrystallites. This single-atom catalyst has extremely high atom efficiency and shows excellent stability and high activity for both CO oxidn. and preferential oxidn. of CO in H2. D. functional theory calcns. show that the high catalytic activity correlates with the partially vacant 5d orbitals of the pos. charged, high-valent Pt atoms, which help to reduce both the CO adsorption energy and the activation barriers for CO oxidn.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXpt1artbY%253D&md5=4e0249ec18ed134d486e450cc0297660
  3. 3
    Nolte, P.; Stierle, A.; Jin-Phillipp, N.; Kasper, N.; Schulli, T.; Dosch, H. Shape Changes of Supported Rh Nanoparticles During Oxidation and Reduction Cycles. Science 2008, 321, 1654– 1658,  DOI: 10.1126/science.1160845
    Google Scholar
    3
    Shape Changes of Supported Rh Nanoparticles During Oxidation and Reduction Cycles
    Nolte, P.; Stierle, A.; Jin-Phillipp, N. Y.; Kasper, N.; Schulli, T. U.; Dosch, H.
    Science (Washington, DC, United States) (2008), 321 (5896), 1654-1658CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
    The microscopic insight into how and why catalytically active nanoparticles change their shape during oxidn. and redn. reactions is a pivotal challenge in the fundamental understanding of heterogeneous catalysis. We report an oxygen-induced shape transformation of rhodium nanoparticles on magnesium oxide (001) substrates that is lifted upon carbon monoxide exposure at 600 K. A Wulff anal. of high-resoln. in situ x-ray diffraction, combined with transmission electron microscopy, shows that this phenomenon is driven by the formation of a oxygen-rhodium-oxygen surface oxide at the rhodium nanofacets. This exptl. access into the behavior of such nanoparticles during a catalytic cycle is useful for the development of improved heterogeneous catalysts.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhtFamtr3O&md5=361b851ab8cb3d650e9b24afbf2d27c3
  4. 4
    Liu, L.; Corma, A. Metal Catalysts for Heterogeneous Catalysis: From Single Atoms to Nanoclusters and Nanoparticles. Chem. Rev. 2018, 118, 4981– 5079,  DOI: 10.1021/acs.chemrev.7b00776
    Google Scholar
    4
    Metal Catalysts for Heterogeneous Catalysis: From Single Atoms to Nanoclusters and Nanoparticles
    Liu, Lichen; Corma, Avelino
    Chemical Reviews (Washington, DC, United States) (2018), 118 (10), 4981-5079CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review. Metal species with different size (single atoms, nanoclusters, and nanoparticles) show different catalytic behavior for various heterogeneous catalytic reactions. It was shown in the literature that many factors including the particle size, shape, chem. compn., metal-support interaction, and metal-reactant/solvent interaction can have significant influences on the catalytic properties of metal catalysts. The recent developments of well-controlled synthesis methodologies and advanced characterization tools allow one to correlate the relations at the mol. level. In this Review, the electronic and geometric structures of single atoms, nanoclusters, and nanoparticles are discussed. Also, the authors will summarize the catalytic applications of single atoms, nanoclusters, and nanoparticles for different types of reactions, including CO oxidn., selective oxidn., selective hydrogenation, org. reactions, electrocatalytic, and photocatalytic reactions. The authors will compare the results obtained from different systems and try to give a picture on how different types of metal species work in different reactions and give perspectives on the future directions toward better understanding of the catalytic behavior of different metal entities (single atoms, nanoclusters, and nanoparticles) in a unifying manner.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXnsFWisro%253D&md5=9dfd32b36e93291725e1b91277cfc1d3
  5. 5
    Nesselberger, M.; Roefzaad, M.; Fayçal Hamou, R.; Ulrich Biedermann, P.; Schweinberger, F. F.; Kunz, S.; Schloegl, K.; Wiberg, G. K.; Ashton, S.; Heiz, U. The Effect of Particle Proximity on the Oxygen Reduction Rate of Size-Selected Platinum Clusters. Nat. Mater. 2013, 12, 919– 924,  DOI: 10.1038/nmat3712
    Google Scholar
    5
    The effect of particle proximity on the oxygen reduction rate of size-selected platinum clusters
    Nesselberger, Markus; Roefzaad, Melanie; Faycal Hamou, R.; Ulrich Biedermann, P.; Schweinberger, Florian F.; Kunz, Sebastian; Schloegl, Katrin; Wiberg, Gustav K. H.; Ashton, Sean; Heiz, Ueli; Mayrhofer, Karl J. J.; Arenz, Matthias
    Nature Materials (2013), 12 (10), 919-924CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
    The diminished surface-area-normalized catalytic activity of highly dispersed Pt nanoparticles compared with bulk Pt is particularly intricate, and not yet understood. Here we report on the oxygen redn. reaction (ORR) activity of well-defined, size-selected Pt nanoclusters; a unique approach that allows precise control of both the cluster size and coverage, independently. Our investigations reveal that size-selected Pt nanoclusters can reach extraordinarily high ORR activities, esp. in terms of mass-normalized activity, if deposited at high coverage on a glassy carbon substrate. It is obsd. that the Pt cluster coverage, and hence the interparticle distance, decisively influence the obsd. catalytic activity and that closely packed assemblies of Pt clusters approach the surface activity of bulk Pt. Our results open up new strategies for the design of catalyst materials that circumvent the detrimental dispersion effect, and may eventually allow the full electrocatalytic potential of Pt nanoclusters to be realized.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhtFCisb%252FN&md5=5d5359906831de55ac9765f1ee676d38
  6. 6
    Turner, M.; Golovko, V. B.; Vaughan, O. P.; Abdulkin, P.; Berenguer-Murcia, A.; Tikhov, M. S.; Johnson, B. F.; Lambert, R. M. Selective Oxidation with Dioxygen by Gold Nanoparticle Catalysts Derived from 55-Atom Clusters. Nature 2008, 454, 981– 983,  DOI: 10.1038/nature07194
    Google Scholar
    6
    Selective oxidation with dioxygen by gold nanoparticle catalysts derived from 55-atom clusters
    Turner, Mark; Golovko, Vladimir B.; Vaughan, Owain P. H.; Abdulkin, Pavel; Berenguer-Murcia, Angel; Tikhov, Mintcho S.; Johnson, Brian F. G.; Lambert, Richard M.
    Nature (London, United Kingdom) (2008), 454 (7207), 981-983CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)
    Supported gold nanoparticles have excited much interest owing to their unusual and somewhat unexpected catalytic properties, but the origin of the catalytic activity is still not fully understood. Exptl. work on gold particles supported on a titanium dioxide (110) single-crystal surface has established a striking size threshold effect assocd. with a metal-to-insulator transition, with gold particles catalytically active only if their diams. fall below ∼3.5 nm. However, the remarkable catalytic behavior might also in part arise from strong electronic interaction between the gold and the titanium dioxide support. In the case of industrially important selective oxidn. reactions, explanation of the effectiveness of gold nanoparticle catalysts is complicated by the need for additives to drive the reaction, and/or the presence of strong support interactions and incomplete understanding of their possible catalytic role. Here we show that very small gold entities (∼1.4 nm) derived from 55-atom gold clusters and supported on inert materials are efficient and robust catalysts for the selective oxidn. of styrene by dioxygen. We find a sharp size threshold in catalytic activity, in that particles with diams. of ∼2 nm and above are completely inactive. Our observations suggest that catalytic activity arises from the altered electronic structure intrinsic to small gold nanoparticles, and that the use of 55-atom gold clusters may prove a viable route to the synthesis of robust gold catalysts suited to practical application.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhtVWns7zO&md5=2eb5ad0e435f48b1215ad2e11e524b66
  7. 7
    Wang, A.; Li, J.; Zhang, T. Heterogeneous Single-Atom Catalysis. Nature Rev. Chem. 2018, 2, 65– 81,  DOI: 10.1038/s41570-018-0010-1
    Google Scholar
    7
    Heterogeneous single-atom catalysis
    Wang, Aiqin; Li, Jun; Zhang, Tao
    Nature Reviews Chemistry (2018), 2 (6), 65-81CODEN: NRCAF7; ISSN:2397-3358. (Nature Research)
    A review. Single-atom catalysis has arguably become the most active new frontier in heterogeneous catalysis. Aided by recent advances in practical synthetic methodologies, characterization techniques and computational modeling, we now have a large no. of single-atom catalysts (SACs) that exhibit distinctive performances for a wide variety of chem. reactions. This Perspective summarizes recent exptl. and computational efforts aimed at understanding the bonding in SACs and how this relates to catalytic performance. The examples described here illustrate the utility of SACs in a broad scope of industrially important reactions and highlight the advantages these catalysts have over those presently used. SACs have well-defined active centers, such that unique opportunities exist for the rational design of new catalysts with high activities, selectivities and stabilities. Indeed, given a certain practical application, we can often design a suitable SAC; thus, the field has developed very rapidly and afforded promising catalyst leads. Moreover, the control we have over certain SAC structures paves the way for designing base metal catalysts with the activities of noble metal catalysts. It appears that we are entering a new era of heterogeneous catalysis in which we have control over well-dispersed single-atom active sites whose properties we can readily tune.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtF2lsr%252FN&md5=2d999a29eb6658f7f9b0b633404dfe6e
  8. 8
    Dvořák, F.; Farnesi Camellone, M.; Tovt, A.; Tran, N. D.; Negreiros, F. R.; Vorokhta, M.; Skála, T.; Matolínová, I.; Mysliveček, J.; Matolín, V. Creating Single-Atom Pt-Ceria Catalysts by Surface Step Decoration. Nat. Commun. 2016, 7, 10801,  DOI: 10.1038/ncomms10801
    Google Scholar
    8
    Creating single-atom Pt-ceria catalysts by surface step decoration
    Dvorak, Filip; Farnesi Camellone, Matteo; Tovt, Andrii; Tran, Nguyen-Dung; Negreiros, Fabio R.; Vorokhta, Mykhailo; Skala, Tomas; Matolinova, Iva; Myslivecek, Josef; Matolin, Vladimir; Fabris, Stefano
    Nature Communications (2016), 7 (), 10801CODEN: NCAOBW; ISSN:2041-1723. (Nature Publishing Group)
    Single-atom catalysts maximize the utilization of supported precious metals by exposing every single metal atom to reactants. To avoid sintering and deactivation at realistic reaction conditions, single metal atoms are stabilized by specific adsorption sites on catalyst substrates. Here we show by combining photoelectron spectroscopy, scanning tunnelling microscopy and d. functional theory calcns. that Pt single atoms on ceria are stabilized by the most ubiquitous defects on solid surfaces-monoat. step edges. Pt segregation at steps leads to stable dispersions of single Pt2+ ions in planar PtO4 moieties incorporating excess O atoms and contributing to oxygen storage capacity of ceria. We exptl. control the step d. on our samples, to maximize the coverage of monodispersed Pt2+ and demonstrate that step engineering and step decoration represent effective strategies for understanding and design of new single-atom catalysts.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xjt1emtL0%253D&md5=6dc5339d021a958f00c3a8af1de885a6
  9. 9
    Yang, X. F.; Wang, A.; Qiao, B.; Li, J.; Liu, J.; Zhang, T. Single-Atom Catalysts: A New Frontier in Heterogeneous Catalysis. Acc. Chem. Res. 2013, 46, 1740– 1748,  DOI: 10.1021/ar300361m
    Google Scholar
    9
    Single-Atom Catalysts: A New Frontier in Heterogeneous Catalysis
    Yang, Xiao-Feng; Wang, Aiqin; Qiao, Botao; Li, Jun; Liu, Jingyue; Zhang, Tao
    Accounts of Chemical Research (2013), 46 (8), 1740-1748CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)
    A review; supported metal nanostructures are the most widely used type of heterogeneous catalyst in industrial processes. The size of metal particles is a key factor in detg. the performance of such catalysts. In particular, because low-coordinated metal atoms often function as the catalytically active sites, the specific activity per metal atom usually increases with decreasing size of the metal particles. However, the surface free energy of metals increases significantly with decreasing particle size, promoting aggregation of small clusters. Using an appropriate support material that strongly interacts with the metal species prevents this aggregation, creating stable, finely dispersed metal clusters with a high catalytic activity, an approach industry has used for a long time. Nevertheless, practical supported metal catalysts are inhomogeneous and usually consist of a mixt. of sizes from nanoparticles to subnanometer clusters. Such heterogeneity not only reduces the metal atom efficiency but also frequently leads to undesired side reactions. It also makes it extremely difficult, if not impossible, to uniquely identify and control the active sites of interest. The ultimate small-size limit for metal particles is the single-atom catalyst (SAC), which contains isolated metal atoms singly dispersed on supports. SACs maximize the efficiency of metal atom use, which is particularly important for supported noble metal catalysts. Moreover, with well-defined and uniform single-atom dispersion, SACs offer great potential for achieving high activity and selectivity. In this Account, we highlight recent advances in prepn., characterization, and catalytic performance of SACs, with a focus on single atoms anchored to metal oxides, metal surfaces, and graphene. We discuss exptl. and theor. studies for a variety of reactions, including oxidn., water gas shift, and hydrogenation. We describe advances in understanding the spatial arrangements and electronic properties of single atoms, as well as their interactions with the support. Single metal atoms on support surfaces provide a unique opportunity to tune active sites and optimize the activity, selectivity, and stability of heterogeneous catalysts, offering the potential for applications in a variety of industrial chem. reactions.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhtVChu73O&md5=2044a224f72851911ecc960a90c6448d
  10. 10
    Grützmacher, H. Cooperating Ligands in Catalysis. Angew. Chem., Int. Ed. 2008, 47, 1814– 1818,  DOI: 10.1002/anie.200704654
    Google Scholar
    10
    Cooperating ligands in catalysis
    Gruetzmacher, Hansjoerg
    Angewandte Chemie, International Edition (2008), 47 (10), 1814-1818CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A review. Cooperating ligands participate directly in bond activation and thereby undergo a reversible chem. transformation. The interplay between metal center and ligand may facilitate a chem. process. In transition-metal-catalyzed reactions, this concept allows the discovery of new chem. reactions, such as the dehydrogenative coupling of primary alcs. and primary amines to amides and mol. hydrogen.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXjtFWhsbs%253D&md5=68febf5124b62a872928c662cd614651
  11. 11
    Boyer, J. L.; Rochford, J.; Tsai, M. K.; Muckerman, J. T.; Fujita, E. Ruthenium Complexes with Non-Innocent Ligands: Electron Distribution and Implications for Catalysis. Coord. Chem. Rev. 2010, 254, 309– 330,  DOI: 10.1016/j.ccr.2009.09.006
    Google Scholar
    11
    Ruthenium complexes with non-innocent ligands: Electron distribution and implications for catalysis
    Boyer, Julie L.; Rochford, Jonathan; Tsai, Ming-Kang; Muckerman, James T.; Fujita, Etsuko
    Coordination Chemistry Reviews (2010), 254 (3-4), 309-330CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)
    A review; ruthenium complexes with the non-innocent ligands (NILs) benzoquinone, iminobenzoquinone and benzoquinonediimine and their redox derivs. exhibit intriguing electronic properties. With the proper ligand set the NIL π* orbitals mix extensively with the ruthenium dπ orbitals resulting in delocalized electron distributions and non-integer oxidn. states, and in most of these systems a particular ruthenium oxidn. state dominates. This review critically examines the electronic structure of Ru-NIL systems from both an exptl. and computational (DFT) perspective. The electron distribution within these complexes can be modulated by altering both the ancillary ligands and the NIL, and in a few cases the resultant electron distributions are exploited for catalysis. The Ru-NIL systems that perform alc. oxidn. and water oxidn. catalysis are discussed in detail. The Tanaka catalyst, an anthracene-bridged dinuclear Ru complex, is an intriguing example of a Ru-NIL framework in catalysis. Unlike other known ruthenium water oxidn. catalysts, the two Ru atoms remain low valent during the catalytic cycle according to DFT calcns., some exptl. evidence, and predictions based on the behavior of the related mononuclear species.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXhsFyjsb3F&md5=a05f310f6650bd565b028866585b232c
  12. 12
    Cargnello, M.; Jaén, J. D.; Garrido, J. H.; Bakhmutsky, K.; Montini, T.; Gámez, J. C.; Gorte, R.; Fornasiero, P. Exceptional Activity for Methane Combustion over Modular Pd@CeO2 Subunits on Functionalized Al2O3. Science 2012, 337, 713– 717,  DOI: 10.1126/science.1222887
    Google Scholar
    12
    Exceptional Activity for Methane Combustion over Modular Pd@CeO2 Subunits on Functionalized Al2O3
    Cargnello, M.; Jaen, J. J. Delgado; Garrido, J. C. Hernandez; Bakhmutsky, K.; Montini, T.; Gamez, J. J. Calvino; Gorte, R. J.; Fornasiero, P.
    Science (Washington, DC, United States) (2012), 337 (6095), 713-717CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
    There is a crit. need for improved methane-oxidn. catalysts to both reduce emissions of methane, a greenhouse gas, and improve the performance of gas turbines. However, materials that are currently available either have low activity below 400°C or are unstable at higher temps. Here, we describe a supramol. approach in which single units composed of a palladium (Pd) core and a ceria (CeO2) shell are preorganized in soln. and then homogeneously deposited onto a modified hydrophobic alumina. Electron microscopy and other structural methods revealed that the Pd cores remained isolated even after heating the catalyst to 850°C. Enhanced metal-support interactions led to exceptionally high methane oxidn., with complete conversion below 400°C and outstanding thermal stability under demanding conditions.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtFCktLbN&md5=738e9df32891d817a6120322358e5207
  13. 13
    Bruix, A.; Rodriguez, J. A.; Ramírez, P. J.; Senanayake, S. D.; Evans, J.; Park, J. B.; Stacchiola, D.; Liu, P.; Hrbek, J.; Illas, F. A New Type of Strong Metal–Support Interaction and the Production of H2 through the Transformation of Water on Pt/CeO2(111) and Pt/CeOx/TiO2(110) Catalysts. J. Am. Chem. Soc. 2012, 134, 8968– 8974,  DOI: 10.1021/ja302070k
    Google Scholar
    13
    A New Type of Strong Metal-Support Interaction and the Production of H2 through the Transformation of Water on Pt/CeO2(111) and Pt/CeOx/TiO2(110) Catalysts
    Bruix, Albert; Rodriguez, Jose A.; Ramirez, Pedro J.; Senanayake, Sanjaya D.; Evans, Jaime; Park, Joon B.; Stacchiola, Dario; Liu, Ping; Hrbek, Jan; Illas, Francesc
    Journal of the American Chemical Society (2012), 134 (21), 8968-8974CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    The electronic properties of Pt nanoparticles deposited on CeO2(111) and CeOx/TiO2(110) model catalysts have been examd. using valence photoemission expts. and d. functional theory (DFT) calcns. The valence photoemission and DFT results point to a new type of "strong metal-support interaction" that produces large electronic perturbations for small Pt particles in contact with ceria and significantly enhances the ability of the admetal to dissoc. the O-H bonds in water. When going from Pt(111) to Pt8/CeO2(111), the dissocn. of water becomes a very exothermic process. The ceria-supported Pt8 appears as a fluxional system that can change geometry and charge distribution to accommodate adsorbates better. In comparison with other water-gas shift (WGS) catalysts [Cu(111), Pt(111), Cu/CeO2(111), and Au/CeO2(111)], the Pt/CeO2(111) surface has the unique property that the admetal is able to dissoc. water in an efficient way. Furthermore, for the codeposition of Pt and CeOx nanoparticles on TiO2(110), we have found a transfer of O from the ceria to Pt that opens new paths for the WGS process and makes the mixed-metal oxide an extremely active catalyst for the prodn. of hydrogen.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38Xms1Slurs%253D&md5=ba371681f5516ef2ba0672d7235805fc
  14. 14
    Su, Y. Q.; Liu, J. X.; Filot, I. A. W.; Hensen, E. J. M. Theoretical Study of Ripening Mechanisms of Pd Clusters on Ceria. Chem. Mater. 2017, 29, 9456– 9462,  DOI: 10.1021/acs.chemmater.7b03555
    Google Scholar
    14
    Ostwald ripening mechanisms of Pd clusters on ceria
    Su, Ya-Qiong; Liu, Jin-Xun; Filot, Ivo A. W.; Hensen, Emiel J. M.
    Chemistry of Materials (2017), 29 (21), 9456-9462CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
    We carried out d. functional theory calcns. to investigate the ripening of Pd clusters on CeO2(111). Starting from stable Pdn clusters (n = 1-21), we compared how these clusters can grow through Ostwald ripening and coalescence. As Pd atoms have mobility higher than that of Pdn clusters on the CeO2(111) surface, Ostwald ripening is predicted to be the dominant sintering mechanism. Particle coalescence is possible only for clusters with less than 5 Pd atoms. These ripening mechanisms are facilitated by adsorbed CO through lowering barriers for the cluster diffusion, detachment of a Pd atom from clusters, and transformation of initial planar clusters.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhs1GrtbbI&md5=947f90456aaa3f11f478886f42a09f6b
  15. 15
    Negreiros, F. R.; Fabris, S. Role of Cluster Morphology in the Dynamics and Reactivity of Subnanometer Pt Clusters Supported on Ceria Surfaces. J. Phys. Chem. C 2014, 118, 21014– 21020,  DOI: 10.1021/jp506404z
    Google Scholar
    15
    Role of Cluster Morphology in the Dynamics and Reactivity of Subnanometer Pt Clusters Supported on Ceria Surfaces
    Negreiros, Fabio R.; Fabris, Stefano
    Journal of Physical Chemistry C (2014), 118 (36), 21014-21020CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    Subnanometer (sub-nm) Pt clusters supported by highly reducible oxide surfaces were studied, and the role of cluster morphol. in the thermodn. and kinetics of surface processes relevant for reactivity, namely cluster mobility, reverse oxygen spillover, and oxygen vacancy formation, was elucidated. The relationships between cluster morphol. and reactivity are rarely considered in computational studies because of the large domain and complexity of the potential energy surface, particularly in the presence of strong metal-support interaction. Global optimization algorithms together with Hubbard-cor. d. functional theory calcns. (DFT + U) are used to identify the stable and metastable morphologies of Pt3-Pt6 clusters supported on pristine and defective CeO2(111) surfaces. This systematic exploration for these sub-nm Pt particles shows that the charge of the supported cluster, its bonding to the substrate, and the degree of ceria redn. depend on the metal/oxide interface area and on the cluster morphol. Concerning reaction thermodn. and kinetics, the use of global optimization methods leads to very different results as compared to usual minimization procedures. By allowing for morphol. changes during reaction, the energetics of reverse O spillover changes from highly endothermic to exothermic and leads to new min.-energy reaction and diffusion mechanisms. The diffusion kinetics predicts clusters as small as Pt6 to be resistant to sintering on ceria surfaces. The relevance of these findings for larger metal clusters and for supporting oxide nanoparticles is discussed as well as their connection with the recent literature.
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  16. 16
    Hansen, T. W.; DeLaRiva, A. T.; Challa, S. R.; Datye, A. K. Sintering of Catalytic Nanoparticles: Particle Migration or Ostwald Ripening?. Acc. Chem. Res. 2013, 46, 1720– 1730,  DOI: 10.1021/ar3002427
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    16
    Sintering of Catalytic Nanoparticles: Particle Migration or Ostwald Ripening?
    Hansen, Thomas W.; De La Riva, Andrew T.; Challa, Sivakumar R.; Datye, Abhaya K.
    Accounts of Chemical Research (2013), 46 (8), 1720-1730CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)
    A review; metal nanoparticles contain the active sites in heterogeneous catalysts, which are important for many industrial applications including the prodn. of clean fuels, chems. and pharmaceuticals, and the cleanup of exhaust from automobiles and stationary power plants. Sintering, or thermal deactivation, is an important mechanism for the loss of catalyst activity. This is esp. true for high temp. catalytic processes, such as steam reforming, automotive exhaust treatment, or catalytic combustion. With dwindling supplies of precious metals and increasing demand, fundamental understanding of catalyst sintering is very important for achieving clean energy and a clean environment, and for efficient chem. conversion processes with atom selectivity. Scientists have proposed two mechanisms for sintering of nanoparticles: particle migration and coalescence (PMC) and Ostwald ripening (OR). PMC involves the mobility of particles in a Brownian-like motion on the support surface, with subsequent coalescence leading to nanoparticle growth. In contrast, OR involves the migration of adatoms or mobile mol. species, driven by differences in free energy and local adatom concns. on the support surface. In this Account, we divide the process of sintering into three phases. Phase I involves rapid loss in catalyst activity (or surface area), phase II is where sintering slows down, and phase III is where the catalyst may reach a stable performance. Much of the previous work is based on inferences from catalysts that were obsd. before and after long term treatments. While the general phenomena can be captured correctly, the mechanisms cannot be detd. Advancements in the techniques of in situ TEM allow us to observe catalysts at elevated temps. under working conditions. We review recent evidence obtained via in situ methods to det. the relative importance of PMC and OR in each of these phases of catalyst sintering. The evidence suggests that, in phase I, OR is responsible for the rapid loss of activity that occurs when particles are very small. Surprisingly, very little PMC is obsd. in this phase. Instead, the rapid loss of activity is caused by the disappearance of the smallest particles. These findings are in good agreement with representative atomistic simulations of sintering. In phase II, sintering slows down since the smallest particles have disappeared. We now see a combination of PMC and OR, but do not fully understand the relative contribution of each of these processes to the overall rates of sintering. In phase III, the particles have grown large and other parasitic phenomena, such as support restructuring, can become important, esp. at high temps. Examg. the evolution of particle size and surface area with time, we do not see a stable or equil. state, esp. for catalysts operating at elevated temps. In conclusion, the recent literature, esp. on in situ studies, shows that OR is the dominant process causing the growth of nanoparticle size. Consequently, this leads to the loss of surface area and activity. While particle migration could be controlled through suitable structuring of catalyst supports, it is more difficult to control the mobility of atomically dispersed species. These insights into the mechanisms of sintering could help to develop sinter-resistant catalysts, with the ultimate goal of designing catalysts that are self-healing.
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  17. 17
    Wang, C.; Gu, X. K.; Yan, H.; Lin, Y.; Li, J.; Liu, D.; Li, W. X.; Lu, J. Water-Mediated Mars–Van Krevelen Mechanism for CO Oxidation on Ceria-Supported Single-Atom Pt Catalyst. ACS Catal. 2017, 7, 887– 891,  DOI: 10.1021/acscatal.6b02685
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    17
    Water-Mediated Mars-Van Krevelen Mechanism for CO Oxidation on Ceria-Supported Single-Atom Pt1 Catalyst
    Wang, Chunlei; Gu, Xiang-Kui; Yan, Huan; Lin, Yue; Li, Junjie; Liu, Dandan; Li, Wei-Xue; Lu, Junling
    ACS Catalysis (2017), 7 (1), 887-891CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
    In water-promoted CO oxidn., water was thought not to directly participate in CO2 prodn. Here we report that via a water-mediated Mars-van Krevelen (MvK) mechanism, water can directly contribute to about 50% of CO2 prodn. on a single-atom Pt1/CeO2 catalyst. The origin is the facile reaction of CO with the hydroxyl from dissocd. water to yield the carboxyl intermediate, which dehydrogenates subsequently with the help of a lattice hydroxyl to generate CO2 and water. The water-mediated MvK type reaction found here provides new insights in the promotion role of water in heterogeneous catalysis.
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  18. 18
    Jones, J.; Xiong, H.; DeLaRiva, A. T.; Peterson, E. J.; Pham, H.; Challa, S. R.; Qi, G.; Oh, S.; Wiebenga, M. H.; Hernández, X. I. P. Thermally Stable Single-AtomPlatinum-on-Ceria Catalysts via Atom Trapping. Science 2016, 353, 150– 154,  DOI: 10.1126/science.aaf8800
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    18
    Thermally stable single-atom platinum-on-ceria catalysts via atom trapping
    Jones, John; Xiong, Haifeng; De La Riva, Andrew T.; Peterson, Eric J.; Pham, Hien; Challa, Sivakumar R.; Qi, Gongshin; Oh, Se; Wiebenga, Michelle H.; Pereira Hernandez, Xavier Isidro; Wang, Yong; Datye, Abhaya K.
    Science (Washington, DC, United States) (2016), 353 (6295), 150-154CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
    Catalysts based on single atoms of scarce precious metals can lead to more efficient use through enhanced reactivity and selectivity. However, single atoms on catalyst supports can be mobile and aggregate into nanoparticles when heated at elevated temps. High temps. are detrimental to catalyst performance unless these mobile atoms can be trapped. We used ceria powders having similar surface areas but different exposed surface facets. When mixed with a platinum/aluminum oxide catalyst and aged in air at 800°C, the platinum transferred to the ceria and was trapped. Polyhedral ceria and nanorods were more effective than ceria cubes at anchoring the platinum. Performing synthesis at high temps. ensures that only the most stable binding sites are occupied, yielding a sinter-resistant, atomically dispersed catalyst.
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  19. 19
    Bruix, A.; Lykhach, Y.; Matolínová, I.; Neitzel, A.; Skála, T.; Tsud, N.; Vorokhta, M.; Stetsovych, V.; Ševčíková, K.; Mysliveček, J. Maximum Noble Metal Efficiency in Catalytic Materials: Atomically Dispersed Surface Platinum. Angew. Chem., Int. Ed. 2014, 53, 10525– 10530,  DOI: 10.1002/anie.201402342
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    There is no corresponding record for this reference.
  20. 20
    Liu, J. C.; Wang, Y. G.; Li, J. Toward Rational Design of Oxide-Supported Single-Atom Catalysts: Atomic Dispersion of Gold on Ceria. J. Am. Chem. Soc. 2017, 139, 6190– 6199,  DOI: 10.1021/jacs.7b01602
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    20
    Toward Rational Design of Oxide-Supported Single-Atom Catalysts: Atomic Dispersion of Gold on Ceria
    Liu, Jin-Cheng; Wang, Yang-Gang; Li, Jun
    Journal of the American Chemical Society (2017), 139 (17), 6190-6199CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    We have constructed a general thermodn. model of chem. potentials and applied ab initio electronic structure and mol. dynamics simulations, as well as kinetic Monte Carlo anal., to probe the dynamical, reactive, and kinetic aspects of metal single-atom catalysts (SACs) on oxide support. We choose Au single atoms (SAs) supported on ceria as a typical example to demonstrate how our model can guide the rational design of highly stable and reactive SACs. It is shown that, under realistic conditions, various factors such as temp., pressure, particle size, and the reducibility of the support can strongly affect both the stability and the reactivity of SACs by altering the relative chem. potentials between SAs and metal nanoparticles (NPs). The Au SAs at step sites of ceria support are rather stable, even at temps. as high as 700 K, and exhibit around 10 orders of magnitude more reactivity for CO oxidn. than the terrace sites. Remarkably, under reaction conditions, Au SAs can be dynamically created at the interface of small-size Au NPs on ceria support even without step sites, which accounts for the puzzling significant size effect in gold catalysis. Our work underscores an unrecognized crit. role of Au SAs in gold nanocatalysis and provides a general methodol. for designing the metal SACs on oxide supports.
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  21. 21
    Ouyang, R.; Liu, J. X.; Li, W. X. Atomistic Theory of Ostwald Ripening and Disintegration of Supported Metal Particles under Reaction Conditions. J. Am. Chem. Soc. 2013, 135, 1760– 1771,  DOI: 10.1021/ja3087054
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    21
    Atomistic Theory of Ostwald Ripening and Disintegration of Supported Metal Particles under Reaction Conditions
    Ouyang, Runhai; Liu, Jin-Xun; Li, Wei-Xue
    Journal of the American Chemical Society (2013), 135 (5), 1760-1771CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Understanding Ostwald ripening and disintegration of supported metal particles under operating conditions has been of central importance in the study of sintering and dispersion of heterogeneous catalysts for long-term industrial implementation. To achieve a quant. description of these complicated processes, an atomistic and generic theory taking into account the reaction environment, particle size and morphol., and metal-support interaction is developed. It includes (1) energetics of supported metal particles, (2) formation of monomers (both the metal adatoms and metal-reactant complexes) on supports, and (3) corresponding sintering rate equations and total activation energies, in the presence of reactants at arbitrary temp. and pressure. The thermodn. criteria for the reactant assisted Ostwald ripening and induced disintegration are formulated, and the influence of reactants on sintering kinetics and redispersion are mapped out. Most energetics and kinetics barriers in the theory can be obtained conveniently by first-principles theory calcns. This allows for the rapid exploration of sintering and disintegration of supported metal particles in huge phase space of structures and compns. under various reaction environments. General strategies of suppressing the sintering of the supported metal particles and facilitating the redispersions of the low surface area catalysts are proposed. The theory is applied to TiO2(110) supported Rh particles in the presence of carbon monoxide, and reproduces well the broad temp., pressure, and particle size range over which the sintering and redispersion occurred in such expts. The result also highlights the importance of the metal-carbonyl complexes as monomers for Ostwald ripening and disintegration of supported metal catalysts in the presence of CO.
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  22. 22
    Berkó, A.; Solymosi, F. Adsorption-Induced Structural Changes of Rh Supported by TiO2(110)-(1× 2): an STM Study. J. Catal. 1999, 183, 91– 101,  DOI: 10.1006/jcat.1998.2368
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    There is no corresponding record for this reference.
  23. 23
    Goldsmith, B. R.; Sanderson, E. D.; Ouyang, R.; Li, W. X. CO-and NO-Induced Disintegration and Redispersion of Three-Way Catalysts Rhodium, Palladium, and Platinum: An ab Initio Thermodynamics Study. J. Phys. Chem. C 2014, 118, 9588– 9597,  DOI: 10.1021/jp502201f
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    23
    CO- and NO-Induced Disintegration and Redispersion of Three-Way Catalysts Rhodium, Palladium, and Platinum: An ab Initio Thermodynamics Study
    Goldsmith, Bryan R.; Sanderson, Evan D.; Ouyang, Runhai; Li, Wei-Xue
    Journal of Physical Chemistry C (2014), 118 (18), 9588-9597CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    Disintegration of supported nanoparticles (NPs) in the presence of reactants can lead to catalyst deactivation or be exploited to redisperse sintered catalysts. To better understand the stability of TiO2(110)-supported three-way catalysts Rh, Pd, and Pt NPs during NOx and CO redn., we present an ab initio thermodn. study of the feasibility for these NPs to disintegrate into adatom-reactant complexes across a large parameter space of temps., pressures, and sizes. The tendencies for disintegration and redispersion between supported Rh, Pd, and Pt NPs are established. Compared to both Pd and Pt, Rh NPs are found to be more susceptible to either NO- or CO-induced disintegration, due to the large and exothermic formation energy of the Rh adatom complexes. Moreover, NO is a more efficient reactant for particle redispersion than CO. These findings provide valuable insights for how to either prevent reactant-induced NP disintegration or facilitate reactant-induced redispersion of sintered catalysts.
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  24. 24
    Suzuki, A.; Inada, Y.; Yamaguchi, A.; Chihara, T.; Yuasa, M.; Nomura, M.; Iwasawa, Y. Time Scale and Elementary Steps of CO-Induced Disintegration of Surface Rhodium Clusters. Angew. Chem., Int. Ed. 2003, 42, 4795– 4799,  DOI: 10.1002/anie.200352318
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    24
    Time scale and elementary steps of CO-induced disintegration of surface rhodium clusters
    Suzuki, Akane; Inada, Yasuhiro; Yamaguchi, Aritomo; Chihara, Teiji; Yuasa, Makoto; Nomura, Masaharu; Iwasawa, Yasuhiro
    Angewandte Chemie, International Edition (2003), 42 (39), 4795-4799CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    While the reaction kinetics and dynamics of mols. adsorbed on catalyst surfaces have been extensively studied, little is known about the dynamic structural change of active metal sites in supported metal cluster/nanoparticle catalysts, such as the time scale of formation and disintegration of the active structure induced by reaction gases and the sequence of bond rearrangements involved in the dynamic event on the surfaces. The in situ time-resolved structural characterization of surface metal clusters and nanoparticles by energy-dispersive x-ray absorption fine structure (DXAFS) is essential to document their dynamic property on an at. basis, which has been a long-term challenge to be addressed. We have succeeded in observing the CO-induced disintegration process of Rh clusters on an Al2O3 surface by DXAFS every 100 ms. Previous static studies on the similar surface phenomenon have been performed by IR, XAFS, and STM, which revealed the structural modification of highly dispersed Rh nanoparticles/Al2O3 catalysts that leads to the formation of isolated Rh(CO)2 species by CO adsorption. The DXAFS technique has been developed and improved to provide in situ structural information on dispersed catalytic materials at a time resoln. of 1 s-several 10 s. Herein, we report novel issues found by the time-resolved DXAFS characterization of the structural disintegrity of Rh clusters on an Al2O3 surface, namely, the time scale and sequence of dynamic bond rearrangements in the clusters and at the interface.
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  25. 25
    Berko, A.; Szökő, J.; Solymosi, F. Effect of CO on the Morphology of Pt Nanoparticles Supported on TiO2(110)-(1× n).. Surf. Sci. 2004, 566, 337– 342,  DOI: 10.1016/j.susc.2004.05.065
    Google Scholar
    There is no corresponding record for this reference.
  26. 26
    Stamatakis, M.; Vlachos, D. G. A Graph-Theoretical Kinetic Monte Carlo Framework for on-Lattice Chemical Kinetics. J. Chem. Phys. 2011, 134, 214115,  DOI: 10.1063/1.3596751
    Google Scholar
    26
    A graph-theoretical kinetic Monte Carlo framework for on-lattice chemical kinetics
    Stamatakis, Michail; Vlachos, Dionisios G.
    Journal of Chemical Physics (2011), 134 (21), 214115/1-214115/13CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
    Existing kinetic Monte Carlo (KMC) frameworks for the simulation of adsorption, desorption, diffusion, and reaction on a lattice often assume that each participating species occupies a single site and represent elementary events involving a max. of two sites. However, these assumptions may be inadequate, esp. in the case of complex chemistries, involving multidentate species or complex coverage and neighboring patterns between several lattice sites. We have developed a novel approach that employs graph-theor. ideas to overcome these challenges and treat easily complex chemistries. As a benchmark, the Ziff-Gulari-Barshad system is simulated and comparisons of the computational times of the graph-theor. KMC and a simpler KMC approach are made. Further, to demonstrate the capabilities of our framework, the water-gas shift chem. on Pt(111) is simulated. (c) 2011 American Institute of Physics.
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  27. 27
    Kresse, G.; Hafner, J. Ab initio Molecular-Dynamics Simulation of the Liquid-Metal–Amorphous-Semiconductor Transition in Germanium. Phys. Rev. B: Condens. Matter Mater. Phys. 1994, 49, 14251,  DOI: 10.1103/PhysRevB.49.14251
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    27
    Ab initio molecular-dynamics simulation of the liquid-metal-amorphous-semiconductor transition in germanium
    Kresse, G.; Hafner, J.
    Physical Review B: Condensed Matter and Materials Physics (1994), 49 (20), 14251-69CODEN: PRBMDO; ISSN:0163-1829.
    The authors present ab initio quantum-mech. mol.-dynamics simulations of the liq.-metal-amorphous-semiconductor transition in Ge. The simulations are based on (a) finite-temp. d.-functional theory of the 1-electron states, (b) exact energy minimization and hence calcn. of the exact Hellmann-Feynman forces after each mol.-dynamics step using preconditioned conjugate-gradient techniques, (c) accurate nonlocal pseudopotentials, and (d) Nose' dynamics for generating a canonical ensemble. This method gives perfect control of the adiabaticity of the electron-ion ensemble and allows the authors to perform simulations over >30 ps. The computer-generated ensemble describes the structural, dynamic, and electronic properties of liq. and amorphous Ge in very good agreement with expt.. The simulation allows the authors to study in detail the changes in the structure-property relation through the metal-semiconductor transition. The authors report a detailed anal. of the local structural properties and their changes induced by an annealing process. The geometrical, bounding, and spectral properties of defects in the disordered tetrahedral network are studied and compared with expt.
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  28. 28
    Blöchl, P. E. Projector Augmented-Wave Method. Phys. Rev. B: Condens. Matter Mater. Phys. 1994, 50, 17953,  DOI: 10.1103/PhysRevB.50.17953
    Google Scholar
    28
    Projector augmented-wave method
    Blochl
    Physical review. B, Condensed matter (1994), 50 (24), 17953-17979 ISSN:0163-1829.
    There is no expanded citation for this reference.
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  29. 29
    Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation mMade Simple. Phys. Rev. Lett. 1996, 77, 3865,  DOI: 10.1103/PhysRevLett.77.3865
    Google Scholar
    There is no corresponding record for this reference.
  30. 30
    Dudarev, S.; Botton, G.; Savrasov, S.; Humphreys, C.; Sutton, A. Electron-Energy-Loss Spectra and the Structural Stability of Nickel Oxide: An LSDA+ U study. Phys. Rev. B: Condens. Matter Mater. Phys. 1998, 57, 1505,  DOI: 10.1103/PhysRevB.57.1505
    Google Scholar
    30
    Electron-energy-loss spectra and the structural stability of nickel oxide: An LSDA+U study
    Dudarev, S. L.; Botton, G. A.; Savrasov, S. Y.; Humphreys, C. J.; Sutton, A. P.
    Physical Review B: Condensed Matter and Materials Physics (1998), 57 (3), 1505-1509CODEN: PRBMDO; ISSN:0163-1829. (American Physical Society)
    By taking better account of electron correlations in the 3d shell of metal ions in Ni oxide it is possible to improve the description of both electron energy loss spectra and parameters characterizing the structural stability of the material compared with local spin d. functional theory.
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  31. 31
    Fabris, S.; de Gironcoli, S.; Baroni, S.; Vicario, G.; Balducci, G. Reply to “Comment on ‘Taming Multiple Valency with Density Functionals: A Case Study of Defective Ceria’. Phys. Rev. B: Condens. Matter Mater. Phys. 2005, 72, 237102,  DOI: 10.1103/PhysRevB.72.237102
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    31
    Reply to "Comment on 'Taming multiple valency with density functionals: A case study of defective ceria' "
    Fabris, Stefano; de Gironcoli, Stefano; Baroni, Stefano; Vicario, Gianpaolo; Balducci, Gabriele
    Physical Review B: Condensed Matter and Materials Physics (2005), 72 (23), 237102/1-237102/2CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
    A polemic in reply to G. Kresse and P. Blaha, ibid, 237101. We address the issues raised in the preceding Comment by discussing the effects of an explicit account of the nonlinear core correction (NLCC) into the Ce pseudopotential employed in our previous calcns. of reduced ceria [Phys. Rev. B 71, 041102(R) (2005)]. At the plain d.-functional-theory (DFT) level, such an account brings our pseudopotential results in good agreement with all-electron ones, which do not predict the insulating character of reduced ceria. At the DFT+U level, the inclusion of the NLCC has no effect on the previously reported electronic structure and equil. geometries. The dependency of the DFT+U energy on the choice of the projector functions defining the Hubbard-U functional is discussed in further detail.
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  32. 32
    Cococcioni, M.; De Gironcoli, S. Linear Response Approach to the Calculation of the Effective Interaction Parameters in the LDA+ U Method. Phys. Rev. B: Condens. Matter Mater. Phys. 2005, 71, 035105,  DOI: 10.1103/PhysRevB.71.035105
    Google Scholar
    32
    Linear response approach to the calculation of the effective interaction parameters in the LDA+U method
    Cococcioni, Matteo; de Gironcoli, Stefano
    Physical Review B: Condensed Matter and Materials Physics (2005), 71 (3), 035105/1-035105/16CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
    We reexamine the LDA + U method of Anisimov and co-workers in the framework of a plane-wave pseudopotential approach. A simplified rotational-invariant formulation is adopted. The calcn. of the Hubbard U entering the expression of the functional is discussed and a linear response approach is proposed that is internally consistent with the chosen definition for the occupation matrix of the relevant localized orbitals. In this way we obtain a scheme whose functionality should not depend strongly on the particular implementation of the model in ab initio calcns. We demonstrate the accuracy of the method, computing structural and electronic properties of a few systems including transition and rare-earth correlated metals, transition metal monoxides, and iron silicate.
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  33. 33
    Castleton, C.; Kullgren, J.; Hermansson, K. Tuning LDA+ U for Electron Localization and Structure at Oxygen Vacancies in Ceria. J. Chem. Phys. 2007, 127, 244704,  DOI: 10.1063/1.2800015
    Google Scholar
    33
    Tuning LDA + U for electron localization and structure at oxygen vacancies in ceria
    Castleton, C. W. M.; Kullgren, J.; Hermansson, K.
    Journal of Chemical Physics (2007), 127 (24), 244704/1-244704/11CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
    We examine the real space structure and the electronic structure (particularly Ce4f electron localization) of oxygen vacancies in CeO2 (ceria) as a function of U in d. functional theory studies with the rotationally invariant forms of the LDA + U and GGA + U functionals. The four nearest neighbor Ce ions always relax outwards, with those not carrying localized Ce4f charge moving furthest. Several quantification schemes show that the charge starts to become localized at U ≈ 3 eV and that the degree of localization reaches a max. at ∼6 eV for LDA + U or at ∼5.5 eV for GGA + U. For higher U it decreases rapidly as charge is transferred onto second neighbor O ions and beyond. The localization is never into at. corelike states; at max. localization about 80-90% of the Ce4f charge is located on the two nearest neighboring Ce ions. However, if we look at the total at. charge we find that the two ions only make a net gain of (0.2-0.4)e each, so localization is actually very incomplete, with localization of Ce4f electrons coming at the expense of moving other electrons off the Ce ions. We have also revisited some properties of defect-free ceria and find that with LDA + U the crystal structure is actually best described with U = 3-4 eV, while the exptl. band structure is obtained with U = 7-8 eV. (For GGA + U the lattice parameters worsen for U > 0 eV, but the band structure is similar to LDA + U.) The best overall choice is U ≈ 6 eV with LDA + U and ≈5.5 eV for GGA + U, since the localization is most important, but a consistent choice for both CeO2 and Ce2O3, with and without vacancies, is hard to find.
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  34. 34
    Da Silva, J. L.; Ganduglia-Pirovano, M. V.; Sauer, J.; Bayer, V.; Kresse, G. Hybrid Functionals Ppplied to Rare-Earth Oxides: The Example of Ceria. Phys. Rev. B: Condens. Matter Mater. Phys. 2007, 75, 045121,  DOI: 10.1103/PhysRevB.75.045121
    Google Scholar
    There is no corresponding record for this reference.
  35. 35
    Henkelman, G.; Jónsson, H. Improved Tangent Estimate in the Nudged Elastic Band Method for Finding Minimum Energy Paths and Saddle Points. J. Chem. Phys. 2000, 113, 9978– 9985,  DOI: 10.1063/1.1323224
    Google Scholar
    35
    Improved tangent estimate in the nudged elastic band method for finding minimum energy paths and saddle points
    Henkelman, Graeme; Jonsson, Hannes
    Journal of Chemical Physics (2000), 113 (22), 9978-9985CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
    An improved way of estg. the local tangent in the nudged elastic band method for finding min. energy paths is presented. In systems where the force along the min. energy path is large compared to the restoring force perpendicular to the path and when many images of the system are included in the elastic band, kinks can develop and prevent the band from converging to the min. energy path. We show how the kinks arise and present an improved way of estg. the local tangent which solves the problem. The task of finding an accurate energy and configuration for the saddle point is also discussed and examples given where a complementary method, the dimer method, is used to efficiently converge to the saddle point. Both methods only require the first deriv. of the energy and can, therefore, easily be applied in plane wave based d.-functional theory calcns. Examples are given from studies of the exchange diffusion mechanism in a Si crystal, Al addimer formation on the Al(100) surface, and dissociative adsorption of CH4 on an Ir(111) surface.
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  36. 36
    Sheppard, D.; Terrell, R.; Henkelman, G. Optimization Methods for Finding Minimum Energy Paths. J. Chem. Phys. 2008, 128, 134106,  DOI: 10.1063/1.2841941
    Google Scholar
    36
    Optimization methods for finding minimum energy paths
    Sheppard, Daniel; Terrell, Rye; Henkelman, Graeme
    Journal of Chemical Physics (2008), 128 (13), 134106/1-134106/10CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
    A comparison of chain-of-states based methods for finding min. energy pathways (MEPs) is presented. In each method, a set of images along an initial pathway between two local min. is relaxed to find a MEP. We compare the nudged elastic band (NEB), doubly nudged elastic band, string, and simplified string methods, each with a set of commonly used optimizers. Our results show that the NEB and string methods are essentially equiv. and the most efficient methods for finding MEPs when coupled with a suitable optimizer. The most efficient optimizer was found to be a form of the limited-memory Broyden-Fletcher-Goldfarb-Shanno method in which the approx. inverse Hessian is constructed globally for all images along the path. The use of a climbing-image allows for finding the saddle point while representing the MEP with as few images as possible. If a highly accurate MEP is desired, it is found to be more efficient to descend from the saddle to the min. than to use a chain-of-states method with many images. Our results are based on a pairwise Morse potential to model rearrangements of a heptamer island on Pt(111), and plane-wave based d. functional theory to model a rollover diffusion mechanism of a Pd tetramer on MgO(100) and dissociative adsorption and diffusion of oxygen on Au(111). (c) 2008 American Institute of Physics.
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  37. 37
    Stamatakis, M. Zacros: Advanced Lattice-KMC Simulation Made Easy; http://www.e-lucid.com/i/software/material_modelling/Zacros.html.
    Google Scholar
    There is no corresponding record for this reference.
  38. 38
    Reuter, K.; Scheffler, M. First-Principles Kinetic Monte Carlo Simulations for Heterogeneous Catalysis: Application to the CO Oxidation at RuO2(110). Phys. Rev. B: Condens. Matter Mater. Phys. 2006, 73, 045433,  DOI: 10.1103/PhysRevB.73.045433
    Google Scholar
    38
    First-principles kinetic Monte Carlo simulations for heterogeneous catalysis: Application to the CO oxidation at RuO2(110)
    Reuter, Karsten; Scheffler, Matthias
    Physical Review B: Condensed Matter and Materials Physics (2006), 73 (4), 045433/1-045433/17CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
    We describe a first-principles statistical mechanics approach enabling us to simulate the steady-state situation of heterogeneous catalysis. In a first step, d.-functional theory together with transition-state theory is employed to obtain the energetics of the relevant elementary processes. Subsequently the statistical mechanics problem is solved by the kinetic Monte Carlo method, which accounts for the correlations, fluctuations, and spatial distributions of the chems. at the surface of the catalyst under steady-state conditions. Applying this approach to the catalytic oxidn. of CO at RuO2(110), we det. the surface at. structure and compn. in reactive environments ranging from ultra-high vacuum (UHV) to technol. relevant conditions, i.e., up to pressures of several atmospheres and elevated temps. We also compute the CO2 formation rates (turnover frequencies). The results are in quant. agreement with all existing exptl. data. We find that the high catalytic activity of this system is intimately connected with a disordered, dynamic surface "phase" with significant compositional fluctuations. In this active state the catalytic function results from a self-regulating interplay of several elementary processes.
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  39. 39
    Pineda, M.; Stamatakis, M. Beyond Mean-Field Approximations for Accurate and Computationally Efficient Models of on-Lattice Chemical Kinetics. J. Chem. Phys. 2017, 147, 024105,  DOI: 10.1063/1.4991690
    Google Scholar
    39
    Beyond mean-field approximations for accurate and computationally efficient models of on-lattice chemical kinetics
    Pineda, M.; Stamatakis, M.
    Journal of Chemical Physics (2017), 147 (2), 024105/1-024105/12CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
    Modeling the kinetics of surface catalyzed reactions is essential for the design of reactors and chem. processes. The majority of microkinetic models employ mean-field approxns., which lead to an approx. description of catalytic kinetics by assuming spatially uncorrelated adsorbates. On the other hand, kinetic Monte Carlo (KMC) methods provide a discrete-space continuous-time stochastic formulation that enables an accurate treatment of spatial correlations in the adlayer, but at a significant computation cost. In this work, we use the so-called cluster mean-field approach to develop higher order approxns. that systematically increase the accuracy of kinetic models by treating spatial correlations at a progressively higher level of detail. We further demonstrate our approach on a reduced model for NO oxidn. incorporating first nearest-neighbor lateral interactions and construct a sequence of approxns. of increasingly higher accuracy, which we compare with KMC and mean-field. The latter is found to perform rather poorly, overestimating the turnover frequency by several orders of magnitude for this system. On the other hand, our approxns., while more computationally intense than the traditional mean-field treatment, still achieve tremendous computational savings compared to KMC simulations, thereby opening the way for employing them in multiscale modeling frameworks. (c) 2017 American Institute of Physics.
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  40. 40
    Eyring, H. The Activated Complex in Chemical Reactions. J. Chem. Phys. 1935, 3, 107– 115,  DOI: 10.1063/1.1749604
    Google Scholar
    40
    Statistical Mechanical Treatment of the Activated Complex in Chemical Reactions
    Eyring, Henry
    Journal of Chemical Physics (1935), 3 (), 107-15CODEN: JCPSA6; ISSN:0021-9606.
    A possible error in Eyring's recent calcns. of abs. reaction rates due to the short life and consequent unsharp quantization of the activated complex is noted. The existence of this error is made more probable by a consideration of the target area required by Eyring's equations at low temps. There is no doubt that his treatment becomes asymptotically correct at high temps.
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  41. 41
    Piccinin, S.; Stamatakis, M. CO Oxidation on Pd (111): a First-Principles-Based Kinetic Monte Carlo Study. ACS Catal. 2014, 4, 2143– 2152,  DOI: 10.1021/cs500377j
    Google Scholar
    41
    CO Oxidation on Pd(111): A First-Principles-Based Kinetic Monte Carlo Study
    Piccinin, Simone; Stamatakis, Michail
    ACS Catalysis (2014), 4 (7), 2143-2152CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
    CO oxidn. on O-precovered Pd(111) surfaces exhibits remarkably different reactivities at different temps., which correlate with structural changes in the at. O overlayer. Stoichiometric titrn. expts. by Nakai et al. (J. Chem. Phys.2006, 124, 224712) show that although the p(2 × 2) ordered phase is inert, the (√3 × √3) and p(2 × 1) phases that form at 320 and 190 K, resp., have different apparent activation energies and reaction orders with respect to O coverage. In this work, we perform first-principles-based kinetic Monte Carlo (kMC) simulations to understand the behavior of this catalytic system and shed light on the origin of the changes in reactivity. Accounting explicitly for lateral interactions among adsorbates and for their impact on the activation energies of the elementary processes, our simulations reproduce quant. the main features of the exptl. measurements, and we show that the relative rates of CO adsorption and surface reaction are different as the temp. changes. We find that ordering of the adsorbate layer strongly depends on the strength of the lateral interactions but does not have a significant role on the catalytic properties of the system.
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  42. 42
    Peleš, S.; Munsky, B.; Khammash, M. Reduction and Solution of the Chemical Master Equation using Time Scale Separation and Finite State Projection. J. Chem. Phys. 2006, 125, 204104,  DOI: 10.1063/1.2397685
    Google Scholar
    42
    Reduction and solution of the chemical master equation using time scale separation and finite state projection
    Peles, Slaven; Munsky, Brian; Khammash, Mustafa
    Journal of Chemical Physics (2006), 125 (20), 204104/1-204104/13CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
    The dynamics of chem. reaction networks often takes place on widely differing time scales-from the order of nanoseconds to the order of several days. This is particularly true for gene regulatory networks, which are modeled by chem. kinetics. Multiple time scales in math. models often lead to serious computational difficulties, such as numerical stiffness in the case of differential equations or excessively redundant Monte Carlo simulations in the case of stochastic processes. A model redn. method is presented for study of stochastic chem. kinetic systems that takes advantage of multiple time scales. The method applies to finite projections of the chem. master equation and allows for effective time scale sepn. of the system dynamics. This method is implemented in a novel numerical algorithm that exploits the time scale sepn. to achieve model order redns. while enabling error checking and control. The efficiency is illustrated of the method in several examples motivated by recent developments in gene regulatory networks.
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  43. 43
    Stamatakis, M.; Vlachos, D. G. Unraveling the Complexity of Catalytic Reactions via Kinetic Monte Carlo simulation: Current Status and Frontiers. ACS Catal. 2012, 2, 2648– 2663,  DOI: 10.1021/cs3005709
    Google Scholar
    43
    Unraveling the Complexity of Catalytic Reactions via Kinetic Monte Carlo Simulation: Current Status and Frontiers
    Stamatakis, Michail; Vlachos, Dionisios G.
    ACS Catalysis (2012), 2 (12), 2648-2663CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
    A review; over the past two decades, the necessity for predictive models of chem. kinetics on catalytic surfaces has motivated the development of ab initio kinetic Monte Carlo (KMC) simulation frameworks. These frameworks have been successfully used to investigate chemistries of academic interest and industrial importance, such as CO oxidn., NO oxidn. and redn., ethylene hydrogenation, CO hydrogenation to ethanol, and water-gas shift. These studies have shed light on the effect of catalyst compn., surface structure, lateral interactions, and operating conditions on the apparent turnover frequency of the chemistries of interest. Yet, extending the existing KMC approaches to study large chemistries on complex catalytic structures poses several challenges. In this review, we discuss the recent milestones in the area of KMC simulation of chem. kinetics on catalytic surfaces and review a no. of studies that have furthered our fundamental understanding of specific chemistries. In addn., we provide directions for future research aiming toward incorporating detailed physics and chem., as well as assessing and improving the accuracy of KMC methods, toward developing quant. models of surface kinetics.
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  44. 44
    Stamatakis, M.; Vlachos, D. G. Equivalence of on-Lattice Stochastic Chemical Kinetics with the Well-Mixed Chemical Master Equation in the Limit of Fast Diffusion. Comput. Chem. Eng. 2011, 35, 2602– 2610,  DOI: 10.1016/j.compchemeng.2011.05.008
    Google Scholar
    44
    Equivalence of on-lattice stochastic chemical kinetics with the well-mixed chemical master equation in the limit of fast diffusion
    Stamatakis, Michail; Vlachos, Dionisios G.
    Computers & Chemical Engineering (2011), 35 (12), 2602-2610CODEN: CCENDW; ISSN:0098-1354. (Elsevier B.V.)
    Well-mixed and lattice-based descriptions of stochastic chem. kinetics were extensively used in the literature. Realizations of the corresponding stochastic processes are obtained by the D. T. Gillespie (1976, 1977) stochastic simulation algorithm and lattice kinetic Monte Carlo algorithms, resp. However, the two frameworks have remained disconnected. The equivalence is shown of these frameworks whereby the stochastic lattice kinetics reduces to effective well-mixed kinetics in the limit of fast diffusion. In the latter, the lattice structure appears implicitly, as the lumped rate of bimol. reactions depends on the no. of neighbors of a site on the lattice. Moreover, a mapping is proposed between the stochastic propensities and the deterministic rates of the well-mixed vessel and lattice dynamics that illustrates the hierarchy of models and the key parameters that enable model redn.
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  45. 45
    Boyer, L.; Broughton, J. Statics and Dynamics of Icosahedrally Twinned and Single-Crystal FCC Clusters. Phys. Rev. B: Condens. Matter Mater. Phys. 1990, 42, 11461,  DOI: 10.1103/PhysRevB.42.11461
    Google Scholar
    There is no corresponding record for this reference.
  46. 46
    Vlachos, D. G.; Schmidt, L. D.; Aris, R. Structures of Small Metal Clusters. i. Low Temperature Behavior. J. Chem. Phys. 1992, 96, 6880– 6890,  DOI: 10.1063/1.462582
    Google Scholar
    There is no corresponding record for this reference.
  47. 47
    Beniya, A.; Isomura, N.; Hirata, H.; Watanabe, Y. Low Temperature Adsorption and Site-Conversion Process of CO on the Ni(111) Surface. Surf. Sci. 2012, 606, 1830– 1836,  DOI: 10.1016/j.susc.2012.07.026
    Google Scholar
    47
    Low temperature adsorption and site-conversion process of CO on the Ni(111) surface
    Beniya, Atsushi; Isomura, Noritake; Hirata, Hirohito; Watanabe, Yoshihide
    Surface Science (2012), 606 (23-24), 1830-1836CODEN: SUSCAS; ISSN:0039-6028. (Elsevier B.V.)
    Low-temp. (25 K) adsorption states and the site conversion of adsorbed CO between the ontop and the hollow sites on Ni(111) were studied by temp. programmed desorption and IR reflection absorption spectroscopy. The activation energy and pre-exponential factor of desorption were estd. to be 1.2 eV and 2.6 × 1013 s-1, resp., in the limit of zero coverage. At low coverage, CO mols. preferentially adsorbed at the hollow sites <100 K. With increasing temp., the ontop sites were also occupied. Using a van't Hoff plot, the enthalpy and the entropy differences between the hollow and ontop CO were estd. to be 36 meV and 0.043 meV K-1, resp., and the vibrational entropy difference was estd. to be 0.085 meV K-1. The pos. entropy difference was the result of the low-energy frustrated translational mode of the ontop CO, which was estd. to be 4.6 meV. With the harmonic approxn., the upper limit of the activation energy of site hopping from ontop sites to hollow sites was estd. to be 61 meV. In addn., it was suggested that the activation energy of hollow-to-hollow site hopping via a bridge site was <37 meV.
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  48. 48
    Ge, Q.; King, D. Surface Diffusion Potential Energy Surfaces from First Principles: CO Chemisorbed on Pt{110}. J. Chem. Phys. 1999, 111, 9461– 9464,  DOI: 10.1063/1.480275
    Google Scholar
    48
    Surface diffusion potential energy surfaces from first principles: CO chemisorbed on Pt{110}
    Ge, Q.; King, D. A.
    Journal of Chemical Physics (1999), 111 (21), 9461-9464CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
    Lateral potential energy curves for the chemisorption of CO on Pt{110} (1×1) and (1×2) along different azimuthal directions were calcd. using d. functional theory slab calcns. In contrast to the simple models almost universally used, the results along 〈110〉 show that there is a barrier of ≈0.15 eV between bridge and atop sites. Both bridge and atop sites are local min. Diffusion along 〈100〉 on the (1×1) surface is strongly inhibited by a barrier ≥1.2 eV. Quasielastic He atom scattering data require reanal. in the light of these results. The free energy, detg. the most stable site at finite temps., includes a significant vibrational entropy term in the atop site.
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  49. 49
    Abild-Pedersen, F.; Andersson, M. CO Adsorption Energies on Metals with Correction for High Coordination Adsorption Sites–A Density Functional Study. Surf. Sci. 2007, 601, 1747– 1753,  DOI: 10.1016/j.susc.2007.01.052
    Google Scholar
    49
    CO adsorption energies on metals with correction for high coordination adsorption sites - A density functional study
    Abild-Pedersen, F.; Andersson, M. P.
    Surface Science (2007), 601 (7), 1747-1753CODEN: SUSCAS; ISSN:0039-6028. (Elsevier B.V.)
    We investigate the accuracy of carbon monoxide adsorption energies and site preferences for the metals Ag, Al, Au, Co, Cu, Fe, Ir, Mo, Ni, Pd, Pt, Re, Rh, Ru, W, and Zn using the RPBE functional with a recently suggested empirical adsorption energy correction for carbon monoxide based on the internal CO stretch vibrational frequency. We find that when including the correction, the adsorption site preference for six of the metals changes, and all adsorption site predictions become accurate. We also collect a large no. of exptl. studies for comparison with our calcd. adsorption energies. The mean abs. deviation including the correction is found to be less than 0.2 eV, showing that the RPBE functional gives a much better quant. agreement between expts. and calcns. than the PW91 functional.
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  50. 50
    Feibelman, P. J.; Hammer, B.; Nørskov, J. K.; Wagner, F.; Scheffler, M.; Stumpf, R.; Watwe, R.; Dumesic, J. The CO/Pt (111) Puzzle. J. Phys. Chem. B 2001, 105, 4018– 4025,  DOI: 10.1021/jp002302t
    Google Scholar
    50
    The CO/Pt(111) Puzzle
    Feibelman, Peter J.; Hammer, B.; Norskov, J. K.; Wagner, F.; Scheffler, M.; Stumpf, R.; Watwe, R.; Dumesic, J.
    Journal of Physical Chemistry B (2001), 105 (18), 4018-4025CODEN: JPCBFK; ISSN:1089-5647. (American Chemical Society)
    Notwithstanding half a dozen theor. publications, well-converged d.- functional calcns., whether based on a local-d. or generalized-gradient exchange-correlation potential, whether all-electron or employing pseudopotentials, underestimate CO's preference for low-coordination binding sites on Pt(111) and vicinals to it. For example, they imply that CO should prefer hollow- to atop-site adsorption on Pt(111), in apparent contradiction to a host of low-temp. exptl. studies.
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  51. 51
    Winterbottom, W. Equilibrium Shape of a Small Particle in Contact with a Foreign Substrate. Acta Metall. 1967, 15, 303– 310,  DOI: 10.1016/0001-6160(67)90206-4
    Google Scholar
    51
    Equilibrium shape of a small particle in contact with a foreign substance
    Winterbottom, Walter L.
    Acta Metallurgica (1967), 15 (2), 303-10CODEN: AMETAR; ISSN:0001-6160.
    A theory was developed for predicting the shapes of particles at interfaces. The analysis indicates that a generalized Gibbs-Wulff construction will predict the shape only when the particle-substrate (or grain boundary) interface is coplanar with the substrate surface (or grain boundary); otherwise, the construction is only an approxn. Application of the technique in the detn. of the γ-plot of Ag under ultrahigh-vacuum conditions was not possible because of the strong binding of the Ag film to the BeO substrates. Films of 99.999% Ag, 3000-5000 A. thick, were evapd. onto small, polished, high purity BeO disks at 25°. Deposition rates were 10 to 20 monolayers/sec.
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  52. 52
    Longwitz, S. R.; Schnadt, J.; Vestergaard, E. K.; Vang, R. T.; Lægsgaard, E.; Stensgaard, I.; Brune, H.; Besenbacher, F. High-Coverage Structures of Carbon Monoxide Adsorbed on Pt(111) Studied by High-Pressure Scanning Tunneling Microscopy. J. Phys. Chem. B 2004, 108, 14497– 14502,  DOI: 10.1021/jp0492218
    Google Scholar
    52
    High-coverage structures of carbon monoxide adsorbed on Pt(111) studied by high-pressure scanning tunneling microscopy
    Longwitz, Sarah R.; Schnadt, Joachim; Vestergaard, Ebbe Kruse; Vang, Ronnie T.; Lgsgaard, Erik; Stensgaard, Ivan; Brune, Harald; Besenbacher, Flemming
    Journal of Physical Chemistry B (2004), 108 (38), 14497-14502CODEN: JPCBFK; ISSN:1520-6106. (American Chemical Society)
    High-pressure scanning tunneling microscopy was used to study the room-temp. adsorption of CO on a Pt(111) single-crystal surface in equil. with the gas phase. The coverage was found to vary continuously, and over the entire range from 10-6-760 Torr pressure-dependent moire patterns were obsd., characteristic of a hexagonal or nearly hexagonal CO overlayer. Two different pressure ranges can be distinguished: below 10-2 Torr, the moire lattice vector is oriented along a 30° high-symmetry direction of the substrate, corresponding to a pressure-dependent rotation of the CO overlayer with respect to the (1 × 1) Pt surface lattice, while above 10-2 Torr, the CO layer angle is independent of the pressure. This behavior is analyzed in terms of the interplay of the repulsive CO-CO interaction potential and the substrate potential.
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  53. 53
    Ertl, G.; Neumann, M.; Streit, K. Chemisorption of CO on the Pt(111) Surface. Surf. Sci. 1977, 64, 393– 410,  DOI: 10.1016/0039-6028(77)90052-8
    Google Scholar
    53
    Chemisorption of carbon monoxide on the platinum(111) surface
    Ertl, G.; Neumann, M.; Streit, K. M.
    Surface Science (1977), 64 (2), 393-410CODEN: SUSCAS; ISSN:0039-6028.
    The system CO/Pt(111) was studied by LEED, thermal desorption, and work function measurements. At 170 K, a √3 × √3/R 30° structure at θ = 1/3 is continuously transformed with increasing coverage into a c4 × 2 structure at θ = 1/2 and finally into a hexagonal close-packed layer with satn. at ∼ θ = 0.68. Due to a decrease of the adsorption energy by ∼ 4 kcal/mol at θ = 0.5 (= 7.5 × 1014 mols./cm2) adsorption is completed at this coverage at room temp. The initial adsorption energy is ∼ 33 kcal/mol. A tendency for disordering below room temp. is shown by the LEED patterns and the Δ.vphi. data. The work function 1st decreases, exhibits a (temp.-dependent) min. at θ = 1/3, attains nearly the value of the clean surface at θ = 1/2, and again exhibits a 2nd (shallow) min. ∼ θ = 0.6. The obsd. effects may be explained by assuming the occupation of 2 adsorption sites at θ ≤ 0.5 with different dipole moments (presumably bridge (A) and 3-fold coordinated (B)) whose adsorption energy differs by only 0.5 kcal/mol. At low temps. at θ = 1/2 sites, A and at θ = 1/3 sites, B are preferentially occupied whereas their small energy difference favor disordering at increasing temp.
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  54. 54
    Kruse Vestergaard, E. K.; Thostrup, P.; An, T.; Lægsgaard, E.; Stensgaard, I.; Hammer, B.; Besenbacher, F. Comment on “High Pressure Adsorbate Structures Studied by Scanning Tunneling Microscopy: CO on Pt(111) in Equilibrium with the Gas Phase. Phys. Rev. Lett. 2002, 88, 259601,  DOI: 10.1103/PhysRevLett.88.259601
    Google Scholar
    There is no corresponding record for this reference.
  55. 55
    Parkinson, G. S.; Novotny, Z.; Argentero, G.; Schmid, M.; Pavelec, J.; Kosak, R.; Blaha, P.; Diebold, U. Carbon Monoxide-Induced Adatom Sintering in a Pd–Fe3O4 Model Catalyst. Nat. Mater. 2013, 12, 724– 728,  DOI: 10.1038/nmat3667
    Google Scholar
    55
    Carbon monoxide-induced adatom sintering in a Pd-Fe3O4 model catalyst
    Parkinson, Gareth S.; Novotny, Zbynek; Argentero, Giacomo; Schmid, Michael; Pavelec, Jiri; Kosak, Rukan; Blaha, Peter; Diebold, Ulrike
    Nature Materials (2013), 12 (8), 724-728CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
    The coarsening of catalytically active metal clusters is often accelerated by the presence of gases, but the role played by gas mols. is difficult to ascertain and varies from system to system. We use scanning tunnelling microscopy to follow the CO-induced coalescence of Pd adatoms supported on the Fe3O4(001) surface at room temp., and find Pd-carbonyl species to be responsible for mobility in this system. Once these reach a crit. d., clusters nucleate; subsequent coarsening occurs through cluster diffusion and coalescence. Whereas CO induces the mobility in the Pd/Fe3O4 system, surface hydroxyls have the opposite effect. Pd atoms transported to surface OH groups are no longer susceptible to carbonyl formation and remain isolated. Following the evolution from well-dispersed metal adatoms into clusters, atom-by-atom, allows identification of the key processes that underlie gas-induced mass transport.
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  56. 56
    Teschner, D.; Wootsch, A.; Pozdnyakova-Tellinger, O.; Kröhnert, J.; Vass, E.; Hävecker, M.; Zafeiratos, S.; Schnörch, P.; Jentoft, P.; Knop-Gericke, A. Partial Pressure Dependent in Situ Spectroscopic Study on the Preferential CO Oxidation in Hydrogen (PROX) over Pt/ceria Catalysts. J. Catal. 2007, 249, 318– 327,  DOI: 10.1016/j.jcat.2007.05.010
    Google Scholar
    56
    Partial pressure dependent in situ spectroscopic study on the preferential CO oxidation in hydrogen (PROX) over Pt/ceria catalysts
    Teschner, D.; Wootsch, A.; Pozdnyakova-Tellinger, O.; Kroehnert, J.; Vass, E. M.; Haevecker, M.; Zafeiratos, S.; Schnoerch, P.; Jentoft, P. C.; Knop-Gericke, A.; Schloegl, R.
    Journal of Catalysis (2007), 249 (2), 318-327CODEN: JCTLA5; ISSN:0021-9517. (Elsevier Ltd.)
    Platinum supported on ceria can oxidize CO in excess hydrogen selectively (PROX process). In situ DRIFTS and high-pressure (∼1 mbar) XPS expts. were performed to study the mechanism of the PROX reaction on Pt/ceria catalysts. The partial pressure of O2 and/or CO was varied and correlated with induced changes in activity and selectivity as well as with the surface state and species under reaction conditions. Pt-carbonyl species changed rather insignificantly, esp. relative to the wide variations of the product pattern with changing feed compn. Furthermore, the interconversion of formate and carbonate species was obsd. Therefore, the changes in the evolution of surface species detected by in situ DRIFTS cannot explain the variation obsd. in CO oxidn. activity. On the other hand, high-pressure XPS showed significant modification of the surface state with changing feed compn. Most significantly, oxygen vacancy formation seemed to correlate with enhanced CO oxidn. activity. At higher vacancy d., water desorption was hindered. Highly hydrated ceria with significant vacancy d. was found to be beneficial for the PROX process; here surface water blocked Hads oxidn. sites. Moreover, lower apparent activation energy of CO oxidn. was measured in the PROX reaction on catalysts with more vacancies. The results given here reinforce the view of catalysts being adaptive to a certain reaction rather than having active sites as prepd. Whereas IR-detectable surface species may only be indicators and/or consequences of this surface change, formation of the beneficial surface/near-surface state may be the rate-limiting factor in several catalytic processes.
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  57. 57
    Wadayama, T.; Todoroki, N.; Yamada, Y.; Sugawara, T.; Miyamoto, K.; Iijama, Y. Oxygen Reduction Reaction Activities of Ni/Pt(111) Model Catalysts Fabricated by Molecular Beam Epitaxy. Electrochem. Commun. 2010, 12, 1112– 1115,  DOI: 10.1016/j.elecom.2010.05.042
    Google Scholar
    57
    Oxygen reduction reaction activities of Ni/Pt(111) model catalysts fabricated by molecular beam epitaxy
    Wadayama, Toshimasa; Todoroki, Naoto; Yamada, Yoshinori; Sugawara, Tatsuya; Miyamoto, Kanji; Iijama, Yuki
    Electrochemistry Communications (2010), 12 (8), 1112-1115CODEN: ECCMF9; ISSN:1388-2481. (Elsevier B.V.)
    O redn. reaction (ORR) activities were evaluated for clean Pt(111) and Ni/Pt(111) model catalysts fabricated by MBE. Exposure of clean Pt(111) to 1.0 L CO at 303 K produced linear-bonded and bridge-bonded CO-Pt IR bands at 2093 and 1858 cm- 1. In contrast, 0.3-nm-thick Ni deposited on Pt(111) at 573 K (573 K-Ni0.3 nm/Pt(111)) produced broad IR bands for adsorbed CO at ∼2070 cm- 1; the sepn. of RHEED streaks is slightly wider for 573 K-Ni0.3 nm/Pt(111) than for the clean Pt(111). For 823 K-Ni0.3nm/Pt(111), the sepn. of the RHEED streaks is the same as that for the Pt(111), and a single sharp IR band due to adsorbed CO is located at 2082 cm- 1. Probably for the 823 K-Ni0.3 nm/Pt(111), a Pt-enriched outermost surface (Pt-skin) was formed through surface segregation of the substrate Pt atoms. ORR activities for the 573 K- and 823 K-Ni0.3 nm/Pt(111) as detd. from linear sweep voltammetry curves were five times and eight times higher than that for clean Pt(111), resp., demonstrating that Pt-skin generation is crucial for developing highly active electrode catalysts for fuel cells.
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  58. 58
    Heyden, B. E.; Bradshaw, A. M. The Adsorption of CO on Pt(111) Studied by Infrared-Reflection-Adsorption Spectroscopy. Surf. Sci. 1983, 125, 787– 802,  DOI: 10.1016/S0039-6028(83)80060-0
    Google Scholar
    There is no corresponding record for this reference.
  59. 59
    McCrea, K.; Parker, J. S.; Chen, P.; Somorjai, G. Surface Structure Sensitivity of High-Pressure CO Dissociation on Pt(557), Pt(100) and Pt(111) Using Sum Frequency Generation Surface Vibrational Spectroscopy. Surf. Sci. 2001, 494, 238– 250,  DOI: 10.1016/S0039-6028(01)01469-8
    Google Scholar
    59
    Surface structure sensitivity of high-pressure CO dissociation on Pt(5 5 7), Pt(1 0 0) and Pt(1 1 1) using sum frequency generation surface vibrational spectroscopy
    McCrea, Keith; Parker, Jessica S.; Chen, Peilin; Somorjai, Gabor
    Surface Science (2001), 494 (3), 238-250CODEN: SUSCAS; ISSN:0039-6028. (Elsevier Science B.V.)
    Using sum frequency generation (SFG) surface vibrational spectroscopy, the interaction of CO and Pt single crystals was investigated at high pressure and high temps. Under 40 Torr of CO, the mol. was found to dissoc. on Pt(1 1 1), Pt(5 5 7), and Pt(1 0 0) at 673, 548, and 500 K, resp. The CO top site frequency was obsd. to shift to lower frequencies as a function of temp. At a particular temp., dependent on the surface structure, the SFG spectra evolved with time, indicating the surface was being modified. The obsd. frequency shift before CO dissocn. is attributed to anharmonic coupling to the frustrated translational mode. At the temp. at which dissocn. occurs, the frequency shift is attributed to surface roughening. The surface roughening is believed to result from the formation of platinum carbonyl species, which would be a driving force to ext. platinum atoms from the surface lattice. For both the (1 1 1) and (1 0 0) surfaces of Pt, the crystal must be heated to a temp. at which platinum carbonyls are formed to produce step and kink sites, which are needed for dissocn. The Pt(1 1 1) surface exhibits a much higher CO dissocn. temp. as compared to Pt(1 0 0) because it is the most stable surface for Pt. Pt(5 5 7) is essentially a (1 1 1) surface with steps already present in the structure, and so the crystal does not need to be heated to a temp. to produce step and kink sites necessary for CO dissocn. through the prodn. of Pt carbonyls. CO can dissoc. on the existing steps of Pt(5 5 7).
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  60. 60
    Gajdoš, M.; Eichler, A.; Hafner, J. CO Adsorption on Close-Packed Transition and Noble Metal Surfaces: Trends from ab initio Calculations. J. Phys.: Condens. Matter 2004, 16, 1141,  DOI: 10.1088/0953-8984/16/8/001
    Google Scholar
    60
    CO adsorption on close-packed transition and noble metal surfaces: trends from ab initio calculations
    Gajdos, Marek; Eichler, Andreas; Hafner, Juergen
    Journal of Physics: Condensed Matter (2004), 16 (8), 1141-1164CODEN: JCOMEL; ISSN:0953-8984. (Institute of Physics Publishing)
    A review. The trends in CO adsorption on close-packed metal surfaces Co, Ni, Cu from the 3d row, Ru, Rh, Pd, Ag from the 4d row and Ir, Pt, Au from the 5d row were studied using d. functional theory. In particular, the trends in adsorption energy, geometry, vibrational properties, and other parameters derived from the electronic structure of the substrate were concerned. The influence of specific changes in our set-up, such as choice of the exchange correlation functional, the choice of pseudopotential, size of the basis set and substrate relaxation, was carefully evaluated. While the geometrical and vibrational properties of the adsorbate-substrate complex are calcd. with high accuracy, the adsorption energies calcd. with the gradient-cor. Perdew-Wang exchange-correlation energies are overestimated. Tn addn., the calcns. tend to favor adsorption sites with higher coordination, resulting in the prediction of the wrong adsorption sites for the Rh, Pt, and Cu surfaces (hollow instead of top). The revised Perdew-Burke-Erzernhof functional (RPBE) leads to lower (i.e. more realistic) adsorption energies for transition metals, but to the wrong results for noble metals-for Ag and Au, endothermic adsorption is predicted. The site preference remains the same. The trends in relation to the electronic structure of the substrate across the periodic table are discussed, summarizing the state-of-the-art of CO adsorption on close-packed metal surfaces.
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  61. 61
    Bazin, P.; Saur, O.; Lavalley, J.; Daturi, M.; Blanchard, G. FT-IR Study of CO Adsorption on Pt/CeO2: Characterisation and Structural Rearrangement of Small Pt Particles. Phys. Chem. Chem. Phys. 2005, 7, 187– 194,  DOI: 10.1039/b414159h
    Google Scholar
    61
    FT-IR study of CO adsorption on Pt/CeO2: characterization and structural rearrangement of small Pt particles
    Bazin, P.; Saur, O.; Lavalley, J. C.; Daturi, M.; Blanchard, G.
    Physical Chemistry Chemical Physics (2005), 7 (1), 187-194CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    CO adsorption has been followed by IR spectroscopy on a Pt/CeO2 sample (Pt loading = 0.5%) treated under oxygen and vacuum or reduced by H2 and then evacuated at various temps. The sample contains highly dispersed Pt. Attention is paid to the presence of an unusual ν(CO) band at 1937 cm-1 on the reduced sample. Such a band is in particular not obsd. when the support is fully covered by CO (CO adsorption at liq. nitrogen temp.) or by methanol, allowing one to assign it to CO bridged species bound to both Pt very lowly coordinated and to the support, e.g. to sites at the periphery of very small Pt particles. Expts. performed after sample redn. at 423 K followed by increasing evacuation temp. between 423 and 673 K showed that the increase of the latter provokes a sintering of the Pt particles, due to ceria surface O2- mobility.
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  62. 62
    Pozdnyakova-Tellinger, O.; Teschner, D.; Kröhnert, J.; Jentoft, F. C.; Knop-Gericke, A.; Schlögl, R.; Wootsch, A. Surface Water-Assisted Preferential CO Oxidation on Pt/CeO2 Catalyst. J. Phys. Chem. C 2007, 111, 5426– 5431,  DOI: 10.1021/jp0669862
    Google Scholar
    62
    Surface Water-Assisted Preferential CO Oxidation on Pt/CeO2 Catalyst
    Pozdnyakova-Tellinger, Olga; Teschner, Detre; Kroehnert, Jutta; Jentoft, Friederike C.; Knop-Gericke, Axel; Schloegl, Robert; Wootsch, Attila
    Journal of Physical Chemistry C (2007), 111 (14), 5426-5431CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    The prodn. of clean hydrogen is a key requirement for a future hydrogen economy, in general, and, specifically, for the application of proton exchange membrane fuel cells (PEMFC). Here, we focus on one of the essential purifn. methods, the so-called preferential oxidn., "PROX" reaction, of traces of CO in a large hydrogen excess. Small platinum particles on a reducible support like ceria are effective to remove CO from hydrogen feed. The paper specifically addresses the mechanism of the PROX reaction on a Pt/CeO2 catalyst using in situ experimentation with time-resolved and temp.-programmed diffuse reflectance IR spectroscopy. Surface species (carbonates, formates, carbonyls, hydroxyls, and adsorbed water) present under reaction conditions are identified, and correlations of their abundance with catalytic performance allow the discrimination between mechanistically relevant species (intermediates) and spectator species. The following scenario is proposed: hydrogen initially adsorbed on platinum spills over to the support, leading to ordered vacancy formation in the ceria bulk as well as hydroxylation and hydration of the surface. CO is mainly adsorbed in on-top orientation on metallic platinum. The linear relationship between the amt. of adsorbed water (H2Oads) and the CO2 prodn. indicates that the hydrated ceria supplies an oxidizing agent at the metal/support interface reacting with the nearby surface carbonyls on the Pt particles yielding CO2. Moreover, adsorbed water also blocks hydrogen oxidn. because of desorption hindrance. From the correlations in the presented results, an intelligent PROX catalyst can be formulated, providing a guideline for future developments.
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  63. 63
    Ding, K.; Gulec, A.; Johnson, A. M.; Schweitzer, N. M.; Stucky, G. D.; Marks, L. D.; Stair, P. C. Identification of Active Sites in CO Oxidation and Water-Gas Shift over Supported Pt Catalysts. Science 2015, 350, 189– 192,  DOI: 10.1126/science.aac6368
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    63
    Identification of active sites in CO oxidation and water-gas shift over supported Pt catalysts
    Ding, Kunlun; Gulec, Ahmet; Johnson, Alexis M.; Schweitzer, Neil M.; Stucky, Galen D.; Marks, Laurence D.; Stair, Peter C.
    Science (Washington, DC, United States) (2015), 350 (6257), 189-192CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
    Identification and characterization of catalytic active sites are the prerequisites for an at.-level understanding of the catalytic mechanism and rational design of high-performance heterogeneous catalysts. Indirect evidence in recent reports suggests that platinum (Pt) single atoms are exceptionally active catalytic sites. We demonstrate that IR spectroscopy can be a fast and convenient characterization method with which to directly distinguish and quantify Pt single atoms from nanoparticles. In addn., we directly observe that only Pt nanoparticles show activity for carbon monoxide (CO) oxidn. and water-gas shift at low temps., whereas Pt single atoms behave as spectators. The lack of catalytic activity of Pt single atoms can be partly attributed to the strong binding of CO mols.
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  64. 64
    Moses-DeBusk, M.; Yoon, M.; Allard, L. F.; Mullins, D. R.; Wu, Z.; Yang, X.; Veith, G.; Stocks, G. M.; Narula, C. K. CO Oxidation on Supported Single Pt Atoms: Experimental and ab initio Density Functional Studies of CO Interaction with Pt atom on θ-Al2O3(010) Surface. J. Am. Chem. Soc. 2013, 135, 12634– 12645,  DOI: 10.1021/ja401847c
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    64
    CO Oxidation on Supported Single Pt Atoms: Experimental and ab Initio Density Functional Studies of CO Interaction with Pt Atom on θ-Al2O3(010) Surface
    Moses-DeBusk, Melanie; Yoon, Mina; Allard, Lawrence F.; Mullins, David R.; Wu, Zili; Yang, Xiaofan; Veith, Gabriel; Stocks, G. Malcolm; Narula, Chaitanya K.
    Journal of the American Chemical Society (2013), 135 (34), 12634-12645CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Although there are only a few known examples of supported single-atom catalysts, they are unique because they bridge the gap between homogeneous and heterogeneous catalysis. Here, we report the CO oxidn. activity of monodisperse single Pt atoms supported on an inert substrate, θ-alumina (Al2O3), in the presence of stoichiometric oxygen. Since CO oxidn. on single Pt atoms cannot occur via a conventional Langmuir-Hinshelwood scheme (L-H scheme) which requires at least one Pt-Pt bond, we carried out a first-principles d. functional theor. study of a proposed pathway which is a variation on the conventional L-H scheme and inspired by the organometallic chem. of platinum. We find that a single supported Pt atom prefers to bond to O2 over CO. CO then bonds with the oxygenated Pt atom and forms a carbonate which dissocs. to liberate CO2, leaving an oxygen atom on Pt. Subsequent reaction with another CO mol. regenerates the single-atom catalyst. The energetics of the proposed mechanism suggests that the single Pt atoms will get covered with CO3 unless the temp. is raised to eliminate CO2. We find evidence for CO3 coverage at room temp. supporting the proposed mechanism in an in situ diffuse reflectance IR study of CO adsorption on the catalyst's supported single atoms. Thus, our results clearly show that supported Pt single atoms are catalytically active and that this catalytic activity can occur without involving the substrate. Characterization by electron microscopy and X-ray absorption studies of the monodisperse Pt/θ-Al2O3 are also presented.
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  65. 65
    Wu, T.; Pan, X.; Zhang, Y.; Miao, Z.; Zhang, B.; Li, J.; Yang, X. Investigation of the Redispersion of Pt Nanoparticles on Polyhedral Ceria Nanoparticles. J. Phys. Chem. Lett. 2014, 5, 2479– 2483,  DOI: 10.1021/jz500839u
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    65
    Investigation of the Redispersion of Pt Nanoparticles on Polyhedral Ceria Nanoparticles
    Wu, Tianxiao; Pan, Xiqiang; Zhang, Yibo; Miao, Zhenzhen; Zhang, Bin; Li, Jingwei; Yang, Xiangguang
    Journal of Physical Chemistry Letters (2014), 5 (14), 2479-2483CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
    Redispersion of Pt nanoparticles on ceria with defined surface planes including cubes ({100}) and octahedra ({111}) has been studied. The Pt redispersion takes place only on ceria cubes in an alternating oxidn. and redn. atm. A quicker alternation rate is beneficial for such redispersion. The authors propose that the redispersion takes place at the moment of alternation of oxidn. and redn.
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  66. 66
    Su, Y. Q.; Filot, I. A. W.; Liu, J. X.; Hensen, E. J. M. Stable Pd-Doped Ceria Structures for CH4 Activation and CO Oxidation. ACS Catal. 2018, 8, 75– 80,  DOI: 10.1021/acscatal.7b03295
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    66
    Stable Pd-Doped Ceria Structures for CH4 Activation and CO Oxidation
    Su, Ya-Qiong; Filot, Ivo A. W.; Liu, Jin-Xun; Hensen, Emiel J. M.
    ACS Catalysis (2018), 8 (1), 75-80CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
    Doping CeO2 with Pd atoms has been assocd. with catalytic CO oxidn., but current surface models do not allow CO adsorption. Here, we report a new structure of Pd-doped CeO2(111), in which Pd adopts a square planar configuration instead of the previously assumed octahedral configuration. Oxygen removal from this doped structure is favorable. The resulting defective Pd-doped CeO2 surface is active for CO oxidn. and is also able to cleave the first C-H bond in methane. We show how the moderate CO adsorption energy and dynamic features of the Pd atom upon CO adsorption and CO oxidn. contribute to a low-barrier catalytic cycle for CO oxidn. These structures, which are also obsd. for Ni and Pt, can lead to a more open coordination environment around the doped-transition-metal center. These thermally stable structures are relevant to the development of single-atom catalysts.
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  67. 67
    Su, Y. Q.; Liu, J. X.; Filot, I. A. W.; Zhang, L.; Hensen, E. J. M. Highly Active and Stable CH4 Oxidation by Substitution of Ce4+ by two Pd2+ Ions in CeO2(111). ACS Catal. 2018, 8, 6552– 6559,  DOI: 10.1021/acscatal.8b01477
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    67
    Highly Active and Stable CH4 Oxidation by Substitution of Ce4+ by Two Pd2+ Ions in CeO2(111)
    Su, Ya-Qiong; Liu, Jin-Xun; Filot, Ivo A. W.; Zhang, Long; Hensen, Emiel J. M.
    ACS Catalysis (2018), 8 (7), 6552-6559CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
    Methane (CH4) combustion is an increasingly important reaction for environmental protection, for which Pd/CeO2 has emerged as the preferred catalyst. There is a lack of understanding of the nature of the active site in these catalysts. Here, we use d. functional theory to understand the role of doping of Pd in the ceria surface for generating sites highly active toward the C-H bonds in CH4. Specifically, we demonstrate that two Pd2+ ions can substitute one Ce4+ ion, resulting in a very stable structure contg. a highly coordinated unsatd. Pd cation that can strongly adsorb CH4 and dissoc. the first C-H bond with a low energy barrier. An important aspect of the high activity of the stabilized isolated Pd cation is its ability to form a strong σ-complex with CH4, which leads to effective activation of CH4. We show that also other transition metals like Pt, Rh, and Ni can give rise to similar structures with high activity toward C-H bond dissocn. These insights provide us with a novel structural view of solid solns. of transition metals such as Pt, Pd, Ni, and Rh in CeO2, known to exhibit high activity in CH4 combustion.
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  68. 68
    Kopelent, R.; van Bokhoven, J. A.; Szlachetko, J.; Edebeli, J.; Paun, C.; Nachtegaal, M.; Safonova, O. V. Catalytically Active and Spectator Ce3+ in Ceria-Supported Metal Catalysts. Angew. Chem. 2015, 127, 8852– 8855,  DOI: 10.1002/ange.201503022
    Google Scholar
    There is no corresponding record for this reference.

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  3. Giovanni Di Liberto, Livia Giordano, Gianfranco Pacchioni. Predicting the Stability of Single-Atom Catalysts in Electrochemical Reactions. ACS Catalysis 2024, 14 (1) , 45-55. https://doi.org/10.1021/acscatal.3c04801
  4. Mina Taleblou, Matteo Farnesi Camellone, Stefano Fabris, Simone Piccinin. CO Oxidation over Platinum Nanoclusters: Unraveling the Role of the Cluster Size and the Supporting Surface. The Journal of Physical Chemistry C 2023, 127 (43) , 21132-21149. https://doi.org/10.1021/acs.jpcc.3c05714
  5. Jonas Amsler, Philipp N. Plessow, Felix Studt, Tomáš Bučko. Anharmonic Correction to Free Energy Barriers from DFT-Based Molecular Dynamics Using Constrained Thermodynamic Integration. Journal of Chemical Theory and Computation 2023, 19 (9) , 2455-2468. https://doi.org/10.1021/acs.jctc.3c00169
  6. Chuanmin Ding, Qingqing Gu, Li-Juan Yu, Shaocheng Zhang, Yafeng Zhang, Zili Ma, Yuanyuan Meng, Hengxuan Zhang, Tao Wang, Junwen Wang, Lichao Ma, Gangsen Li, Bing Yang, Tao Zhang. Reversible Transformation and Distribution Determination of Diverse Pt Single-Atom Species. Journal of the American Chemical Society 2023, 145 (4) , 2523-2531. https://doi.org/10.1021/jacs.2c12106
  7. Tao Ban, Xi-Yang Yu, Hao-Zhe Kang, Zheng-Qing Huang, Jun Li, Chun-Ran Chang. Design of SA-FLP Dual Active Sites for Nonoxidative Coupling of Methane. ACS Catalysis 2023, 13 (2) , 1299-1309. https://doi.org/10.1021/acscatal.2c04479
  8. Jeremy Hu, Eun Mi Kim, Michael J. Janik, Konstantinos Alexopoulos. Hydrogen Activation and Spillover on Anatase TiO2-Supported Ag Single-Atom Catalysts. The Journal of Physical Chemistry C 2022, 126 (17) , 7482-7491. https://doi.org/10.1021/acs.jpcc.2c01670
  9. Wantong Zhao, Zun Guan, Debao Li, Baojun Wang, Maohong Fan, Riguang Zhang. Syngas Conversion to C2 Species over WC and M/WC (M = Cu or Rh) Catalysts: Identifying the Function of Surface Termination and Supported Metal Type. ACS Applied Materials & Interfaces 2022, 14 (17) , 19491-19504. https://doi.org/10.1021/acsami.2c02217
  10. Alexandre C. Foucher, Shengsong Yang, Daniel J. Rosen, Jennifer D. Lee, Renjing Huang, Zhiqiao Jiang, Francisco G. Barrera, Kelly Chen, George G. Hollyer, Cynthia M. Friend, Raymond J. Gorte, Christopher B. Murray, Eric A. Stach. Synthesis and Characterization of Core-Shell Cu-Ru, Cu-Rh, and Cu-Ir Nanoparticles. Journal of the American Chemical Society 2022, 144 (17) , 7919-7928. https://doi.org/10.1021/jacs.2c02538
  11. Baljeet Singh, Manoj B. Gawande, Arun D. Kute, Rajender S. Varma, Paolo Fornasiero, Peter McNeice, Rajenahally V. Jagadeesh, Matthias Beller, Radek Zbořil. Single-Atom (Iron-Based) Catalysts: Synthesis and Applications. Chemical Reviews 2021, 121 (21) , 13620-13697. https://doi.org/10.1021/acs.chemrev.1c00158
  12. Gerhard R. Wittreich, Geun Ho Gu, Daniel J. Robinson, Markos A. Katsoulakis, Dionisios G. Vlachos. Uncertainty Quantification and Error Propagation in the Enthalpy and Entropy of Surface Reactions Arising from a Single DFT Functional. The Journal of Physical Chemistry C 2021, 125 (33) , 18187-18196. https://doi.org/10.1021/acs.jpcc.1c04754
  13. Yubing Lu, Shulan Zhou, Chun-Te Kuo, Deepak Kunwar, Coogan Thompson, Adam S. Hoffman, Alexey Boubnov, Sen Lin, Abhaya K. Datye, Hua Guo, Ayman M. Karim. Unraveling the Intermediate Reaction Complexes and Critical Role of Support-Derived Oxygen Atoms in CO Oxidation on Single-Atom Pt/CeO2. ACS Catalysis 2021, 11 (14) , 8701-8715. https://doi.org/10.1021/acscatal.1c01900
  14. Jonas Amsler, Philipp N. Plessow, Felix Studt, Tomáš Bučko. Anharmonic Correction to Adsorption Free Energy from DFT-Based MD Using Thermodynamic Integration. Journal of Chemical Theory and Computation 2021, 17 (2) , 1155-1169. https://doi.org/10.1021/acs.jctc.0c01022
  15. Youchao Kong, Di Liu, Haoqiang Ai, Kin Ho Lo, Shuangpeng Wang, Hui Pan. Theoretical Screening of Single Atoms Supported on Two-Dimensional Nb2CN2 for Nitrogen Fixation. ACS Applied Nano Materials 2020, 3 (11) , 11274-11281. https://doi.org/10.1021/acsanm.0c02380
  16. Yifan Wang, Ya-Qiong Su, Emiel J. M. Hensen, Dionisios G. Vlachos. Finite-Temperature Structures of Supported Subnanometer Catalysts Inferred via Statistical Learning and Genetic Algorithm-Based Optimization. ACS Nano 2020, 14 (10) , 13995-14007. https://doi.org/10.1021/acsnano.0c06472
  17. Zhaozhuo Yu, Hongguo Wu, Yan Li, Yufei Xu, Hu Li, Song Yang. Advances in Heterogeneously Catalytic Degradation of Biomass Saccharides with Ordered-Nanoporous Materials. Industrial & Engineering Chemistry Research 2020, 59 (39) , 16970-16986. https://doi.org/10.1021/acs.iecr.0c01625
  18. Kang Rui Garrick Lim, Albertus D. Handoko, Srinivasa Kartik Nemani, Brian Wyatt, Hai-Ying Jiang, Junwang Tang, Babak Anasori, Zhi Wei Seh. Rational Design of Two-Dimensional Transition Metal Carbide/Nitride (MXene) Hybrids and Nanocomposites for Catalytic Energy Storage and Conversion. ACS Nano 2020, 14 (9) , 10834-10864. https://doi.org/10.1021/acsnano.0c05482
  19. Jonas Amsler, Bidyut B. Sarma, Giovanni Agostini, Gonzalo Prieto, Philipp N. Plessow, Felix Studt. Prospects of Heterogeneous Hydroformylation with Supported Single Atom Catalysts. Journal of the American Chemical Society 2020, 142 (11) , 5087-5096. https://doi.org/10.1021/jacs.9b12171
  20. Xin Liu, Meng Xu, Lingyun Wan, Hongdan Zhu, Kexin Yao, Roberto Linguerri, Gilberte Chambaud, Yu Han, Changgong Meng. Superior Catalytic Performance of Atomically Dispersed Palladium on Graphene in CO Oxidation. ACS Catalysis 2020, 10 (5) , 3084-3093. https://doi.org/10.1021/acscatal.9b04840
  21. Yucong Huang, Jingjing Xiong, Zhigang Zou, Zhongxin Chen. Emerging Strategies for the Synthesis of Correlated Single Atom Catalysts. Advanced Materials 2025, 37 (2) https://doi.org/10.1002/adma.202312182
  22. Kehao Zhang, Yuran Han, Beibei Wang, Huanhuan Shi, Hailong Wang, Shixiang Gao, Qingguo Huang. Tailoring of orderly CeO2/Pt loaded Ti4O7 reactive electrochemical membranes for efficient electrooxidation of antimicrobial dichlorophen. Chemical Engineering Journal 2024, 496 , 153969. https://doi.org/10.1016/j.cej.2024.153969
  23. Dongyuan Liu, Houyu Zhu, Xiaoxiao Gong, Yucheng Fan, Zhennan Liu, Xiaohan Li, Xin Wang, Wen Zhao, Hao Ren, Wenyue Guo. Boosting CO oxidation performance via reaction-induced single-atom active site: DFT and microkinetic investigation of a unified CO oxidation mechanism on Gd-doped ceria supported copper catalysts. Journal of Rare Earths 2024, 358 https://doi.org/10.1016/j.jre.2024.09.015
  24. Zeyi Zhang, Wei Wu, Suhao Chen, Zichen Wang, Yangyang Tan, Wei Chen, Fei Guo, Runzhe Chen, Niancai Cheng. Directed Dual Charge Pumping Tunes the d ‐Orbital Configuration of Pt Cluster Boosting Hydrogen Evolution Kinetic. Small 2024, 20 (22) https://doi.org/10.1002/smll.202307135
  25. Dongyuan Liu, Houyu Zhu, Xiaoxiao Gong, Saifei Yuan, Hao Ma, Ping He, Yucheng Fan, Wen Zhao, Hao Ren, Wenyue Guo. Understanding and controlling the formation of single-atom site from supported Cu10 cluster by tuning CeO2 reducibility: Theoretical insight into the Gd-doping effect on electronic metal-support interaction. Journal of Colloid and Interface Science 2024, 661 , 720-729. https://doi.org/10.1016/j.jcis.2024.01.174
  26. Tao Ban, Xi-Yang Yu, Hai-Kuo Tian, Zheng-Qing Huang, Chun-Ran Chang. One-step conversion of methane and formaldehyde to ethanol over SA-FLP dual-active-site catalysts: A DFT study. Chinese Chemical Letters 2024, 35 (4) , 108549. https://doi.org/10.1016/j.cclet.2023.108549
  27. Laihao Liu, Tiankai Chen, Zhongxin Chen. Understanding the Dynamic Aggregation in Single‐Atom Catalysis. Advanced Science 2024, 11 (13) https://doi.org/10.1002/advs.202308046
  28. Cheoulwoo Oh, Chulwan Lim, Man Ho Han, Kwan-Young Lee, Jae-Young Choi, Keun Hwa Chae, Hyung-Suk Oh, Woong Hee Lee. Observing N in Co-Nx-C during cathodic reaction via operando X-ray spectroscopy. Applied Surface Science 2024, 648 , 158991. https://doi.org/10.1016/j.apsusc.2023.158991
  29. Liping Liu, Coogan B. Thompson, Tianyou Mou, Ayman M. Karim, Hongliang Xin. Elucidation of site structures and CO oxidation kinetics of the Ir1/TiO2 single-atom catalyst. Chem Catalysis 2024, 4 (2) , 100900. https://doi.org/10.1016/j.checat.2024.100900
  30. Haoyu Liu, Yanran Cui, Minglu Zhu, Yugang Fu, Yue Sun, Zhen Meng, Bo Peng, Lei Nie. Incorporation of Ag on stable Pt/CeO2 for low-temperature active and high-temperature stable CO oxidation catalyst. Molecular Catalysis 2024, 553 , 113704. https://doi.org/10.1016/j.mcat.2023.113704
  31. Shedrack G. Akpe, Sun Hee Choi, Hyung Chul Ham. First-principles study on the design of nickel based bimetallic catalysts for xylose to xylitol conversion. Physical Chemistry Chemical Physics 2023, 26 (1) , 352-364. https://doi.org/10.1039/D3CP03503D
  32. Giovanni Di Liberto, Gianfranco Pacchioni. Modeling Single‐Atom Catalysis. Advanced Materials 2023, 35 (46) https://doi.org/10.1002/adma.202307150
  33. Xinyi Duan, Yu Han, Beien Zhu, Yi Gao. Modelling of metal nanoparticles’ structures and dynamics under reaction conditions. Materials Today Catalysis 2023, 3 , 100032. https://doi.org/10.1016/j.mtcata.2023.100032
  34. Wei Liu, Yiwen Zhang, Mengyan Wang, Hui Sheng, Ben Wang, Huafang Li, Yanxia Zhao, Liguo Wang, Guozhu Chen, Zhongpeng Wang. The coupling synergy of active Pt species and oxygen vacancy induced by PtCu for enhanced performance towards the removal of NO and CO. Journal of Catalysis 2023, 426 , 101-112. https://doi.org/10.1016/j.jcat.2023.07.005
  35. Weijie Yang, Binghui Zhou, Liugang Chen, Ruiyang Shi, Hao Li, Xiaoshuo Liu, Zhengyang Gao. Coordination engineering for single-atom catalysts in bifunctional oxidation NO and mercury. Fuel 2023, 349 , 128751. https://doi.org/10.1016/j.fuel.2023.128751
  36. Shiyan Cao, Sulei Hu, Wei-Xue Li. First-principles thermodynamics study of CO/OH induced disintegration of precious metal nanoparticles on TiO2(110). Chinese Journal of Chemical Physics 2023, 36 (4) , 411-418. https://doi.org/10.1063/1674-0068/cjcp2207111
  37. XueQian Xiao, Xiao Hu, Qiming Liu, Yuling Zhang, Guo-Jun Zhang, Shaowei Chen. Single-atom nanozymes as promising catalysts for biosensing and biomedical applications. Inorganic Chemistry Frontiers 2023, 10 (15) , 4289-4312. https://doi.org/10.1039/D3QI00430A
  38. Yingchong Huang, Shuxuan Liu, Tuyuan Zhu, Chunyan Zhou, Zhanguo Jiang, Xuehui Gao. Electrocatalytic Meralorganic Frameworks and OER Based on Metal-organic Frameworks and their Structure. 2023, 86-128. https://doi.org/10.2174/9789815136029123010005
  39. Juwon Kim, Danwon Lee, Chihyun Nam, Jinkyu Chung, Bonho Koo, Namdong Kim, Jongwoo Lim. Energy material analysis via in-situ/operando scanning transmission x-ray microscopy: A review. Journal of Electron Spectroscopy and Related Phenomena 2023, 266 , 147337. https://doi.org/10.1016/j.elspec.2023.147337
  40. Dong Yun Shin, Dong-Hee Lim. DFT investigation into efficient transition metal single-atom catalysts supported on N-doped graphene for nitrate reduction reactions. Chemical Engineering Journal 2023, 468 , 143466. https://doi.org/10.1016/j.cej.2023.143466
  41. Xiaoming Zhang, Zhangxun Xia, Huanqiao Li, Shansheng Yu, Suli Wang, Gongquan Sun. Structure evolution and durability of Metal-Nitrogen-Carbon (M = Co, Ru, Rh, Pd, Ir) based oxygen evolution reaction electrocatalyst: A theoretical study. Journal of Colloid and Interface Science 2023, 640 , 170-178. https://doi.org/10.1016/j.jcis.2023.02.103
  42. Shedrack G. Akpe, Sun Hee Choi, Hyung Chul Ham. Direct C–C bond scission of xylitol to ethylene and propylene glycol precursors using single-atom catalysts (SACs) anchored on MgO. APL Materials 2023, 11 (5) https://doi.org/10.1063/5.0146265
  43. Leilei Wang, Hengwei Wang, Junling Lu. Local chemical environment effect in single-atom catalysis. Chem Catalysis 2023, 3 (4) , 100492. https://doi.org/10.1016/j.checat.2022.100492
  44. Yong Wu, Huimin Guo, Xin Liu, Changgong Meng. Evolution of Graphene Supported Ru N (N=1–4) Clusters in CO Atmosphere: A First‐Principles Investigation. European Journal of Inorganic Chemistry 2023, 26 (9) https://doi.org/10.1002/ejic.202200719
  45. Yu Yin, Lei Shi, Shu Zhang, Xiaoguang Duan, Jinqiang Zhang, Hongqi Sun, Shaobin Wang. Two−dimensional nanomaterials confined single atoms: New opportunities for environmental remediation. Nano Materials Science 2023, 5 (1) , 15-38. https://doi.org/10.1016/j.nanoms.2022.07.001
  46. Eunji Kang, Jungwoo Choi, Hyuk Choi, Jieun Yun, Ju Hyeok Lee, Mi Yoo, Chunjoong Kim, Hyuck Mo Lee, Hyun You Kim. Gold single-atoms confined at the CeO x -TiO 2 interfaces with enhanced low-temperature activity toward CO oxidation. Nanotechnology 2023, 34 (4) , 045703. https://doi.org/10.1088/1361-6528/ac9b61
  47. Zhuochun Huang, Yingying Cao, Dandan Chen, Li-Long Zhang, Hu Li. Mechanistic insight into surface oxygen species of the polyoxometalate-supported Pd single-atom catalysts for highly efficient CO oxidation. Molecular Catalysis 2023, 534 , 112802. https://doi.org/10.1016/j.mcat.2022.112802
  48. Xilin Zhang, Wenli Kang, Xiaodong Li, Qianqian Peng, Zongxian Yang, Weichao Wang. A density functional theory study of the CO oxidation on Pt1 supported on PtX2 (X = S, Se, Te). Applied Surface Science 2023, 609 , 155341. https://doi.org/10.1016/j.apsusc.2022.155341
  49. Mingzhi Wang, Yige Zhang, Zhuangzhuang Wu, Yanping Zheng, Zhaohui Zhou, Weizheng Weng. Redox dynamics of platinum species on CeO2 during CO oxidation reaction. Chemical Engineering Journal 2022, 450 , 138171. https://doi.org/10.1016/j.cej.2022.138171
  50. Wei Tan, Shaohua Xie, Duy Le, Weijian Diao, Meiyu Wang, Ke-Bin Low, Dave Austin, Sampyo Hong, Fei Gao, Lin Dong, Lu Ma, Steven N. Ehrlich, Talat S. Rahman, Fudong Liu. Fine-tuned local coordination environment of Pt single atoms on ceria controls catalytic reactivity. Nature Communications 2022, 13 (1) https://doi.org/10.1038/s41467-022-34797-2
  51. Ping Yan, Song Shu, Xian Shi, Jianjun Li. Promotion effect of Au single-atom support graphene for CO oxidation. Chinese Chemical Letters 2022, 33 (11) , 4822-4827. https://doi.org/10.1016/j.cclet.2022.01.032
  52. Hai-Cai Huang, Ting-Ting Wang, Jun Li, Jing Chen, Yuxiang Bu, Shi-Bo Cheng. A strain-engineered self-intercalation Ta9Se12 based bifunctional single atom catalyst for oxygen evolution and reduction reactions. Applied Surface Science 2022, 602 , 154378. https://doi.org/10.1016/j.apsusc.2022.154378
  53. Haotian Zhang, Siyuan Fang, Yun Hang Hu. Recent advances in single-atom catalysts for CO oxidation. Catalysis Reviews 2022, 64 (3) , 491-532. https://doi.org/10.1080/01614940.2020.1821443
  54. Zhongxin Chen, Jia Liu, Ming Joo Koh, Kian Ping Loh. Single‐Atom Catalysis: From Simple Reactions to the Synthesis of Complex Molecules. Advanced Materials 2022, 34 (25) https://doi.org/10.1002/adma.202103882
  55. Qi Wang, Juhui Gong, Heng Zhang, Qi-Yuan Fan, Lei Xue, Jinfang Wu, Jiaxin Li, Yan Wang, Ze Liu, Rui Gao, Shanghong Zeng. Co-promotion of two-type active sites: PtCu single-atom alloy and copper-ceria interface for preferential oxidation of CO. Applied Catalysis B: Environmental 2022, 306 , 121117. https://doi.org/10.1016/j.apcatb.2022.121117
  56. Huimin Liu, Yuqiao Li, Xavier Djitcheu, Lequan Liu. Recent advances in single-atom catalysts for thermally driven reactions. Chemical Engineering Science 2022, 255 , 117654. https://doi.org/10.1016/j.ces.2022.117654
  57. Baisong Chang, Liqin Zhang, Shaolong Wu, Ziyan Sun, Zhen Cheng. Engineering single-atom catalysts toward biomedical applications. Chemical Society Reviews 2022, 51 (9) , 3688-3734. https://doi.org/10.1039/D1CS00421B
  58. Doan Pham Minh, Philippe Serp. Introduction to Supported Metal Single Atom Catalysis. 2022, 1-49. https://doi.org/10.1002/9783527830169.ch1
  59. Lu Chen, Xin-Ping Wu, Xue-Qing Gong. Unique catalytic mechanisms of methanol dehydrogenation at Pd-doped ceria: A DFT+U study. The Journal of Chemical Physics 2022, 156 (13) https://doi.org/10.1063/5.0085913
  60. M. Pineda, M. Stamatakis. Kinetic Monte Carlo simulations for heterogeneous catalysis: Fundamentals, current status, and challenges. The Journal of Chemical Physics 2022, 156 (12) https://doi.org/10.1063/5.0083251
  61. Yang Mu, Tingting Wang, Jian Zhang, Changgong Meng, Yifu Zhang, Zongkui Kou. Single-Atom Catalysts: Advances and Challenges in Metal-Support Interactions for Enhanced Electrocatalysis. Electrochemical Energy Reviews 2022, 5 (1) , 145-186. https://doi.org/10.1007/s41918-021-00124-4
  62. Ya-Qiong Su, Yan-Yang Qin, Tiantian Wu, De-Yin Wu. Structure sensitivity of ceria-supported Au catalysts for CO oxidation. Journal of Catalysis 2022, 407 , 353-363. https://doi.org/10.1016/j.jcat.2022.02.008
  63. Yuxing Xu, Bei Li, Jiafei Zhang, Ge Bai, Xiaolong Zhang, Qinglan Hao, Yahao Wang, Xiaoshun Zhou, Botao Teng, Xingchen Liu. Exploration of Metal-Molecule interaction of subnanometric heterogeneous catalysts via simulated Raman spectrum. Applied Surface Science 2022, 579 , 152194. https://doi.org/10.1016/j.apsusc.2021.152194
  64. Huimin Liu, Qinglei Liu, Yarong Wang, Yongfei Wang, Shulei Chou, Zhizhi Hu, Zhiqiang Zhang. Bifunctional carbon-based cathode catalysts for zinc-air battery: A review. Chinese Chemical Letters 2022, 33 (2) , 683-692. https://doi.org/10.1016/j.cclet.2021.07.038
  65. Priyanka Aggarwal, Debasish Sarkar, Kamlendra Awasthi, Prashanth W. Menezes. Functional role of single-atom catalysts in electrocatalytic hydrogen evolution: Current developments and future challenges. Coordination Chemistry Reviews 2022, 452 , 214289. https://doi.org/10.1016/j.ccr.2021.214289
  66. Albert Bruix. Activating catalysts by adsorbate-induced reconstructions. Nature Catalysis 2022, 5 (2) , 84-85. https://doi.org/10.1038/s41929-022-00742-1
  67. Subhajit Sarkar, Ashmita Biswas, Ramendra Sundar Dey. Oxygen reduction reaction by non-noble metal-based catalysts. 2022, 205-239. https://doi.org/10.1016/B978-0-323-88508-9.00005-7
  68. Min Chen, Jianhua Chen, Chuncheng Chen, Changbin Zhang, Hong He. Distinct photocatalytic charges separation pathway on CuOx modified rutile and anatase TiO2 under visible light. Applied Catalysis B: Environmental 2022, 300 , 120735. https://doi.org/10.1016/j.apcatb.2021.120735
  69. Jiaojiao Zhao, Yurong He, Fei Wang, Yusen Yang, Wentao Zheng, Chunfang Huo, Haijun Jiao, Yong Yang, Yongwang Li, Xiaodong Wen. A recyclable CoGa intermetallic compound catalyst for the hydroformylation reaction. Journal of Catalysis 2021, 404 , 244-249. https://doi.org/10.1016/j.jcat.2021.09.031
  70. Shedrack G. Akpe, Sun Hee Choi, Hyung Chul Ham. Conversion of cyclic xylose into xylitol on Ru, Pt, Pd, Ni, and Rh catalysts: a density functional theory study. Physical Chemistry Chemical Physics 2021, 23 (46) , 26195-26208. https://doi.org/10.1039/D1CP04660H
  71. Gopal K. Dixit, Manish Kumar, Ankita Katiyar, Antonius P. J. Jansen, Alexander P. van Bavel, Ravi Agrawal, Prathamesh M. Shenai, Varadharajan Srinivasan. Unraveling the activity of iron carbide clusters embedded in silica for thermocatalytic conversion of methane. Catalysis Science & Technology 2021, 11 (22) , 7398-7411. https://doi.org/10.1039/D1CY01229K
  72. Cheng Yang, Zongyan Zhao, Qingju Liu. Mechanistic insight into the dispersion behavior of single platinum atom on monolayer g-C3N4 in single-atom catalysts from density functional theory calculations. Applied Surface Science 2021, 566 , 150697. https://doi.org/10.1016/j.apsusc.2021.150697
  73. M.A. Salaev, A.A. Salaeva, T.S. Kharlamova, G.V. Mamontov. Pt–CeO2-based composites in environmental catalysis: A review. Applied Catalysis B: Environmental 2021, 295 , 120286. https://doi.org/10.1016/j.apcatb.2021.120286
  74. Yan‐Yang Qin, Ya‐Qiong Su. A DFT Study on Heterogeneous Pt/CeO 2 (110) Single Atom Catalysts for CO Oxidation. ChemCatChem 2021, 13 (17) , 3857-3863. https://doi.org/10.1002/cctc.202100643
  75. Junwei Chen, Zuqiao Ou, Haixin Chen, Shuqin Song, Kun Wang, Yi Wang. Recent developments of nanocarbon based supports for PEMFCs electrocatalysts. Chinese Journal of Catalysis 2021, 42 (8) , 1297-1326. https://doi.org/10.1016/S1872-2067(20)63736-6
  76. Ilya Yu. Titov, Viktor S. Stroylov, PolinaV. Rusina, Igor V. Svitanko. Preliminary modelling as the first stage of targeted organic synthesis. Russian Chemical Reviews 2021, 90 (7) , 831-867. https://doi.org/10.1070/RCR5012
  77. Andrei I. Boronin, Elena M. Slavinskaya, Alberto Figueroba, Andrey I. Stadnichenko, Tatyana Yu. Kardash, Olga A. Stonkus, Elizaveta A. Fedorova, Valerii V. Muravev, Valery A. Svetlichnyi, Albert Bruix, Konstantin M. Neyman. CO oxidation activity of Pt/CeO2 catalysts below 0 °C: platinum loading effects. Applied Catalysis B: Environmental 2021, 286 , 119931. https://doi.org/10.1016/j.apcatb.2021.119931
  78. Valery Muravev, Giulia Spezzati, Ya-Qiong Su, Alexander Parastaev, Fu-Kuo Chiang, Alessandro Longo, Carlos Escudero, Nikolay Kosinov, Emiel J. M. Hensen. Interface dynamics of Pd–CeO2 single-atom catalysts during CO oxidation. Nature Catalysis 2021, 4 (6) , 469-478. https://doi.org/10.1038/s41929-021-00621-1
  79. Ting‐Hsun Yang, Po‐Chun Han, I‐Ta Wang, Celine H. Chen, M. A. Majeed Khan, Cheng‐Yen Wen, Kevin C.‐W. Wu. Water‐Based Synthesis of Gold Single Atoms‐Embedded, Metal–Organic Frameworks‐Derived Nanoporous Carbon Nanoparticles with Enhanced Reduction Ability. Advanced Materials Interfaces 2021, 8 (8) https://doi.org/10.1002/admi.202001638
  80. Baljeet Singh, Vikas Sharma, Rahul P. Gaikwad, Paolo Fornasiero, Radek Zbořil, Manoj B. Gawande. Single‐Atom Catalysts: A Sustainable Pathway for the Advanced Catalytic Applications. Small 2021, 17 (16) https://doi.org/10.1002/smll.202006473
  81. Bu-Tong Li, Jiao-Jiao Jiang, Lu-Lin Li, Ju Peng. Thermal stability and detonation character of nitroso-substituted derivatives of cubane. Molecular Physics 2021, 119 (6) , e1834157. https://doi.org/10.1080/00268976.2020.1834157
  82. Ya-Qiong Su, Long Zhang, Yifan Wang, Jin-Xun Liu, Valery Muravev, Konstantinos Alexopoulos, Ivo A. W. Filot, Dionisios G. Vlachos, Emiel J. M. Hensen. Stability of heterogeneous single-atom catalysts: a scaling law mapping thermodynamics to kinetics. npj Computational Materials 2020, 6 (1) https://doi.org/10.1038/s41524-020-00411-6
  83. Lulu Li, Xin Chang, Xiaoyun Lin, Zhi-Jian Zhao, Jinlong Gong. Theoretical insights into single-atom catalysts. Chemical Society Reviews 2020, 49 (22) , 8156-8178. https://doi.org/10.1039/D0CS00795A
  84. Zhongxin Song, Lei Zhang, Kieran Doyle‐Davis, Xianzhu Fu, Jing‐Li Luo, Xueliang Sun. Recent Advances in MOF‐Derived Single Atom Catalysts for Electrochemical Applications. Advanced Energy Materials 2020, 10 (38) https://doi.org/10.1002/aenm.202001561
  85. Zhongxin Song, Ya‐Nan Zhu, Hanshuo Liu, Mohammad Norouzi Banis, Lei Zhang, Junjie Li, Kieran Doyle‐Davis, Ruying Li, Tsun‐Kong Sham, Lijun Yang, Alan Young, Gianluigi A. Botton, Li‐Min Liu, Xueliang Sun. Engineering the Low Coordinated Pt Single Atom to Achieve the Superior Electrocatalytic Performance toward Oxygen Reduction. Small 2020, 16 (43) https://doi.org/10.1002/smll.202003096
  86. Sikai Wang, Ning Yan. X-ray Absorption Spectroscopy: An Indispensable Tool to Study Single-Atom Catalysts. Synchrotron Radiation News 2020, 33 (5) , 18-26. https://doi.org/10.1080/08940886.2020.1812354
  87. Minttu M. Kauppinen, Marko M. Melander, Karoliina Honkala. First-principles insight into CO hindered agglomeration of Rh and Pt single atoms on m -ZrO 2. Catalysis Science & Technology 2020, 10 (17) , 5847-5855. https://doi.org/10.1039/D0CY00413H
  88. Francis Doherty, Hui Wang, Ming Yang, Bryan R. Goldsmith. Nanocluster and single-atom catalysts for thermocatalytic conversion of CO and CO 2. Catalysis Science & Technology 2020, 10 (17) , 5772-5791. https://doi.org/10.1039/D0CY01316A
  89. Bolin Wang, Yuxue Yue, Chunxiao Jin, Jinyue Lu, Saisai Wang, Lu Yu, Lingling Guo, Rongrong Li, Zhong-Ting Hu, Zhiyan Pan, Jia Zhao, Xiaonian Li. Hydrochlorination of acetylene on single-atom Pd/N-doped carbon catalysts: Importance of pyridinic-N synergism. Applied Catalysis B: Environmental 2020, 272 , 118944. https://doi.org/10.1016/j.apcatb.2020.118944
  90. Haoxiang Xu, Daojian Cheng. First-principles-aided thermodynamic modeling of transition-metal heterogeneous catalysts: A review. Green Energy & Environment 2020, 5 (3) , 286-302. https://doi.org/10.1016/j.gee.2020.07.006
  91. Butong Li, Lulin Li, Ting Luo. Theoretical exploration about the thermal stability and detonation properties of nitro-substituted hypoxanthine. Journal of Molecular Modeling 2020, 26 (6) https://doi.org/10.1007/s00894-020-04391-8
  92. Ya-Qiong Su, Long Zhang, Valery Muravev, Emiel J.M. Hensen. Lattice oxygen activation in transition metal doped ceria. Chinese Journal of Catalysis 2020, 41 (6) , 977-984. https://doi.org/10.1016/S1872-2067(19)63468-6
  93. Mi Yoo, Young-Sang Yu, Hyunwoo Ha, Siwon Lee, Jin-Seok Choi, Sunyoung Oh, Eunji Kang, Hyuk Choi, Hyesung An, Kug-Seung Lee, Jeong Young Park, Richard Celestre, Matthew A. Marcus, Kasra Nowrouzi, Doug Taube, David A. Shapiro, WooChul Jung, Chunjoong Kim, Hyun You Kim. A tailored oxide interface creates dense Pt single-atom catalysts with high catalytic activity. Energy & Environmental Science 2020, 13 (4) , 1231-1239. https://doi.org/10.1039/C9EE03492G
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  95. Jingyue Liu. Single-atom catalysis for a sustainable and greener future. Current Opinion in Green and Sustainable Chemistry 2020, 22 , 54-64. https://doi.org/10.1016/j.cogsc.2020.01.004
  96. Ning Cao, Mao Fei Ran, Yanyan Feng, Wei Chu, Chengfa Jiang, Wenjing Sun, Congmei Chen. Density functional theory study of N-doping effect on the stability and activity of Pd/NCNT catalysts for heck reaction. Applied Surface Science 2020, 506 , 144960. https://doi.org/10.1016/j.apsusc.2019.144960
  97. Qiang Wan, Victor Fung, Sen Lin, Zili Wu, De-en Jiang. Perovskite-supported Pt single atoms for methane activation. Journal of Materials Chemistry A 2020, 8 (8) , 4362-4368. https://doi.org/10.1039/C9TA11712A
  98. Weijie Yang, Mingliang Zhao, Xunlei Ding, Kai Ma, Chongchong Wu, Ian D. Gates, Zhengyang Gao. The effect of coordination environment on the kinetic and thermodynamic stability of single-atom iron catalysts. Physical Chemistry Chemical Physics 2020, 22 (7) , 3983-3989. https://doi.org/10.1039/C9CP05349B
  99. Huijing Xiang, Wei Feng, Yu Chen. Single‐Atom Catalysts in Catalytic Biomedicine. Advanced Materials 2020, 32 (8) https://doi.org/10.1002/adma.201905994
  100. Zhuole Lu, Shwetank Yadav, Chandra Veer Singh. Predicting aggregation energy for single atom bimetallic catalysts on clean and O* adsorbed surfaces through machine learning models. Catalysis Science & Technology 2020, 10 (1) , 86-98. https://doi.org/10.1039/C9CY02070E
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Cite this: ACS Catal. 2019, 9, 4, 3289–3297
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https://doi.org/10.1021/acscatal.9b00252
Published March 5, 2019

Copyright © 2019 American Chemical Society. This publication is licensed under CC-BY-NC-ND.

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  • Abstract

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    Figure 1

    Figure 1. Schematic illustration of the relative stability of Pt SAs and NPs on CeO2 in the presence of adsorbed CO molecules.

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    Figure 2

    Figure 2. (a) Computed CO adsorption energy on Pt(111) and Pt(100) facets as a function of the CO coverage and (b) CO coverage at given temperature and CO partial pressure for Pt(111).

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    Figure 3

    Figure 3. Critical size diagrams of the supported Pt NPs with respect to the thermodynamic stability as a function of temperature and CO partial pressure relative to isolated Pt SAs (a) on the terrace of CeO2(111) with nonwetting and (b) wetting, (c) on the step-edges of CeO2(111), and (d) on the terrace of CeO2(100). Gray area relates to Pt NPs with less than 38 atoms, which were not considered in this study.

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    Figure 4

    Figure 4. Pt SAs located at a CeO2(111) step before (a) and after (b) O2 dissociation, and (c–f) doped into the CeO2(111) surface (color code: white, Ce; gray, irrelevant O; red, relevant O; black, C; blue, Pt). (g) Ab initio-determined phase diagram of the Pt-doped CeO2(111) surface.

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    Figure 5

    Figure 5. CO oxidation pathways by Pt SAs on CeO2(111), on stepped CeO2(111), and doped in the CeO2(111) surface.

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    Figure 6

    Figure 6. (a) Arrhenius plot of the rate of CO oxidation on three types of Pt SA on ceria. (b–d) Steady-state coverages of dominant surface states of Pt SAs on CeO2(111) during CO oxidation (p = 0.1 atm, CO/O2 ratio = 2).

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  • References

    This article references 68 other publications.

    1. 1
      Nie, L.; Mei, D.; Xiong, H.; Peng, B.; Ren, Z.; Hernandez, X. I. P.; DeLaRiva, A.; Wang, M.; Engelhard, M. H.; Kovarik, L. Activation of Surface Lattice Oxygen in Single-Atom Pt/CeO2 for Low-Temperature CO Oxidation. Science 2017, 358, 1419– 1423,  DOI: 10.1126/science.aao2109
      1
      Activation of surface lattice oxygen in single-atom Pt/CeO2 for low temperature CO oxidation
      Nie, Lei; Mei, Donghai; Xiong, Haifeng; Peng, Bo; Ren, Zhibo; Hernandez, Xavier Isidro Pereira; De La Riva, Andrew; Wang, Meng; Engelhard, Mark H.; Kovarik, Libor; Datye, Abhaya K.; Wang, Yong
      Science (Washington, DC, United States) (2017), 358 (6369), 1419-1423CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
      To improve fuel efficiency, advanced combustion engines are being designed to minimize the amt. of heat wasted in the exhaust. Hence, future generations of catalysts must perform at temps. that are 100° lower than current exhaust-treatment catalysts. Achieving low-temp. activity, while surviving the harsh conditions encountered at high engine loads, remains a formidable challenge. Atomically dispersed ionic Pt (Pt2+) on ceria (CeO2), which is already thermally stable, can be activated via steam treatment (at 750°) to simultaneously achieve the goals of low-temp. CO oxidn. activity while providing outstanding hydrothermal stability. A new type of active site is created on CeO2 in the vicinity of Pt2+, which provides the improved reactivity. These active sites are stable up to 800° in oxidizing environments.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhvFGmtr%252FM&md5=2aa1525b0c0fe9271ce995d7e2f8d454
    2. 2
      Qiao, B.; Wang, A.; Yang, X.; Allard, L. F.; Jiang, Z.; Cui, Y.; Liu, J.; Li, J.; Zhang, T. Single-Atom Catalysis of CO Oxidation Using Pt1/FeOx. Nat. Chem. 2011, 3, 634– 641,  DOI: 10.1038/nchem.1095
      2
      Single-atom catalysis of CO oxidation using Pt1/FeOx
      Qiao, Botao; Wang, Aiqin; Yang, Xiaofeng; Allard, Lawrence F.; Jiang, Zheng; Cui, Yitao; Liu, Jingyue; Li, Jun; Zhang, Tao
      Nature Chemistry (2011), 3 (8), 634-641CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)
      Platinum-based heterogeneous catalysts are crit. to many important com. chem. processes, but their efficiency is extremely low on a per metal atom basis, because only the surface active-site atoms are used. Catalysts with single-atom dispersions are thus highly desirable to maximize atom efficiency, but making them is challenging. Here we report the synthesis of a single-atom catalyst that consists of only isolated single Pt atoms anchored to the surfaces of iron oxide nanocrystallites. This single-atom catalyst has extremely high atom efficiency and shows excellent stability and high activity for both CO oxidn. and preferential oxidn. of CO in H2. D. functional theory calcns. show that the high catalytic activity correlates with the partially vacant 5d orbitals of the pos. charged, high-valent Pt atoms, which help to reduce both the CO adsorption energy and the activation barriers for CO oxidn.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXpt1artbY%253D&md5=4e0249ec18ed134d486e450cc0297660
    3. 3
      Nolte, P.; Stierle, A.; Jin-Phillipp, N.; Kasper, N.; Schulli, T.; Dosch, H. Shape Changes of Supported Rh Nanoparticles During Oxidation and Reduction Cycles. Science 2008, 321, 1654– 1658,  DOI: 10.1126/science.1160845
      3
      Shape Changes of Supported Rh Nanoparticles During Oxidation and Reduction Cycles
      Nolte, P.; Stierle, A.; Jin-Phillipp, N. Y.; Kasper, N.; Schulli, T. U.; Dosch, H.
      Science (Washington, DC, United States) (2008), 321 (5896), 1654-1658CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
      The microscopic insight into how and why catalytically active nanoparticles change their shape during oxidn. and redn. reactions is a pivotal challenge in the fundamental understanding of heterogeneous catalysis. We report an oxygen-induced shape transformation of rhodium nanoparticles on magnesium oxide (001) substrates that is lifted upon carbon monoxide exposure at 600 K. A Wulff anal. of high-resoln. in situ x-ray diffraction, combined with transmission electron microscopy, shows that this phenomenon is driven by the formation of a oxygen-rhodium-oxygen surface oxide at the rhodium nanofacets. This exptl. access into the behavior of such nanoparticles during a catalytic cycle is useful for the development of improved heterogeneous catalysts.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhtFamtr3O&md5=361b851ab8cb3d650e9b24afbf2d27c3
    4. 4
      Liu, L.; Corma, A. Metal Catalysts for Heterogeneous Catalysis: From Single Atoms to Nanoclusters and Nanoparticles. Chem. Rev. 2018, 118, 4981– 5079,  DOI: 10.1021/acs.chemrev.7b00776
      4
      Metal Catalysts for Heterogeneous Catalysis: From Single Atoms to Nanoclusters and Nanoparticles
      Liu, Lichen; Corma, Avelino
      Chemical Reviews (Washington, DC, United States) (2018), 118 (10), 4981-5079CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review. Metal species with different size (single atoms, nanoclusters, and nanoparticles) show different catalytic behavior for various heterogeneous catalytic reactions. It was shown in the literature that many factors including the particle size, shape, chem. compn., metal-support interaction, and metal-reactant/solvent interaction can have significant influences on the catalytic properties of metal catalysts. The recent developments of well-controlled synthesis methodologies and advanced characterization tools allow one to correlate the relations at the mol. level. In this Review, the electronic and geometric structures of single atoms, nanoclusters, and nanoparticles are discussed. Also, the authors will summarize the catalytic applications of single atoms, nanoclusters, and nanoparticles for different types of reactions, including CO oxidn., selective oxidn., selective hydrogenation, org. reactions, electrocatalytic, and photocatalytic reactions. The authors will compare the results obtained from different systems and try to give a picture on how different types of metal species work in different reactions and give perspectives on the future directions toward better understanding of the catalytic behavior of different metal entities (single atoms, nanoclusters, and nanoparticles) in a unifying manner.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXnsFWisro%253D&md5=9dfd32b36e93291725e1b91277cfc1d3
    5. 5
      Nesselberger, M.; Roefzaad, M.; Fayçal Hamou, R.; Ulrich Biedermann, P.; Schweinberger, F. F.; Kunz, S.; Schloegl, K.; Wiberg, G. K.; Ashton, S.; Heiz, U. The Effect of Particle Proximity on the Oxygen Reduction Rate of Size-Selected Platinum Clusters. Nat. Mater. 2013, 12, 919– 924,  DOI: 10.1038/nmat3712
      5
      The effect of particle proximity on the oxygen reduction rate of size-selected platinum clusters
      Nesselberger, Markus; Roefzaad, Melanie; Faycal Hamou, R.; Ulrich Biedermann, P.; Schweinberger, Florian F.; Kunz, Sebastian; Schloegl, Katrin; Wiberg, Gustav K. H.; Ashton, Sean; Heiz, Ueli; Mayrhofer, Karl J. J.; Arenz, Matthias
      Nature Materials (2013), 12 (10), 919-924CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
      The diminished surface-area-normalized catalytic activity of highly dispersed Pt nanoparticles compared with bulk Pt is particularly intricate, and not yet understood. Here we report on the oxygen redn. reaction (ORR) activity of well-defined, size-selected Pt nanoclusters; a unique approach that allows precise control of both the cluster size and coverage, independently. Our investigations reveal that size-selected Pt nanoclusters can reach extraordinarily high ORR activities, esp. in terms of mass-normalized activity, if deposited at high coverage on a glassy carbon substrate. It is obsd. that the Pt cluster coverage, and hence the interparticle distance, decisively influence the obsd. catalytic activity and that closely packed assemblies of Pt clusters approach the surface activity of bulk Pt. Our results open up new strategies for the design of catalyst materials that circumvent the detrimental dispersion effect, and may eventually allow the full electrocatalytic potential of Pt nanoclusters to be realized.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhtFCisb%252FN&md5=5d5359906831de55ac9765f1ee676d38
    6. 6
      Turner, M.; Golovko, V. B.; Vaughan, O. P.; Abdulkin, P.; Berenguer-Murcia, A.; Tikhov, M. S.; Johnson, B. F.; Lambert, R. M. Selective Oxidation with Dioxygen by Gold Nanoparticle Catalysts Derived from 55-Atom Clusters. Nature 2008, 454, 981– 983,  DOI: 10.1038/nature07194
      6
      Selective oxidation with dioxygen by gold nanoparticle catalysts derived from 55-atom clusters
      Turner, Mark; Golovko, Vladimir B.; Vaughan, Owain P. H.; Abdulkin, Pavel; Berenguer-Murcia, Angel; Tikhov, Mintcho S.; Johnson, Brian F. G.; Lambert, Richard M.
      Nature (London, United Kingdom) (2008), 454 (7207), 981-983CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)
      Supported gold nanoparticles have excited much interest owing to their unusual and somewhat unexpected catalytic properties, but the origin of the catalytic activity is still not fully understood. Exptl. work on gold particles supported on a titanium dioxide (110) single-crystal surface has established a striking size threshold effect assocd. with a metal-to-insulator transition, with gold particles catalytically active only if their diams. fall below ∼3.5 nm. However, the remarkable catalytic behavior might also in part arise from strong electronic interaction between the gold and the titanium dioxide support. In the case of industrially important selective oxidn. reactions, explanation of the effectiveness of gold nanoparticle catalysts is complicated by the need for additives to drive the reaction, and/or the presence of strong support interactions and incomplete understanding of their possible catalytic role. Here we show that very small gold entities (∼1.4 nm) derived from 55-atom gold clusters and supported on inert materials are efficient and robust catalysts for the selective oxidn. of styrene by dioxygen. We find a sharp size threshold in catalytic activity, in that particles with diams. of ∼2 nm and above are completely inactive. Our observations suggest that catalytic activity arises from the altered electronic structure intrinsic to small gold nanoparticles, and that the use of 55-atom gold clusters may prove a viable route to the synthesis of robust gold catalysts suited to practical application.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhtVWns7zO&md5=2eb5ad0e435f48b1215ad2e11e524b66
    7. 7
      Wang, A.; Li, J.; Zhang, T. Heterogeneous Single-Atom Catalysis. Nature Rev. Chem. 2018, 2, 65– 81,  DOI: 10.1038/s41570-018-0010-1
      7
      Heterogeneous single-atom catalysis
      Wang, Aiqin; Li, Jun; Zhang, Tao
      Nature Reviews Chemistry (2018), 2 (6), 65-81CODEN: NRCAF7; ISSN:2397-3358. (Nature Research)
      A review. Single-atom catalysis has arguably become the most active new frontier in heterogeneous catalysis. Aided by recent advances in practical synthetic methodologies, characterization techniques and computational modeling, we now have a large no. of single-atom catalysts (SACs) that exhibit distinctive performances for a wide variety of chem. reactions. This Perspective summarizes recent exptl. and computational efforts aimed at understanding the bonding in SACs and how this relates to catalytic performance. The examples described here illustrate the utility of SACs in a broad scope of industrially important reactions and highlight the advantages these catalysts have over those presently used. SACs have well-defined active centers, such that unique opportunities exist for the rational design of new catalysts with high activities, selectivities and stabilities. Indeed, given a certain practical application, we can often design a suitable SAC; thus, the field has developed very rapidly and afforded promising catalyst leads. Moreover, the control we have over certain SAC structures paves the way for designing base metal catalysts with the activities of noble metal catalysts. It appears that we are entering a new era of heterogeneous catalysis in which we have control over well-dispersed single-atom active sites whose properties we can readily tune.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtF2lsr%252FN&md5=2d999a29eb6658f7f9b0b633404dfe6e
    8. 8
      Dvořák, F.; Farnesi Camellone, M.; Tovt, A.; Tran, N. D.; Negreiros, F. R.; Vorokhta, M.; Skála, T.; Matolínová, I.; Mysliveček, J.; Matolín, V. Creating Single-Atom Pt-Ceria Catalysts by Surface Step Decoration. Nat. Commun. 2016, 7, 10801,  DOI: 10.1038/ncomms10801
      8
      Creating single-atom Pt-ceria catalysts by surface step decoration
      Dvorak, Filip; Farnesi Camellone, Matteo; Tovt, Andrii; Tran, Nguyen-Dung; Negreiros, Fabio R.; Vorokhta, Mykhailo; Skala, Tomas; Matolinova, Iva; Myslivecek, Josef; Matolin, Vladimir; Fabris, Stefano
      Nature Communications (2016), 7 (), 10801CODEN: NCAOBW; ISSN:2041-1723. (Nature Publishing Group)
      Single-atom catalysts maximize the utilization of supported precious metals by exposing every single metal atom to reactants. To avoid sintering and deactivation at realistic reaction conditions, single metal atoms are stabilized by specific adsorption sites on catalyst substrates. Here we show by combining photoelectron spectroscopy, scanning tunnelling microscopy and d. functional theory calcns. that Pt single atoms on ceria are stabilized by the most ubiquitous defects on solid surfaces-monoat. step edges. Pt segregation at steps leads to stable dispersions of single Pt2+ ions in planar PtO4 moieties incorporating excess O atoms and contributing to oxygen storage capacity of ceria. We exptl. control the step d. on our samples, to maximize the coverage of monodispersed Pt2+ and demonstrate that step engineering and step decoration represent effective strategies for understanding and design of new single-atom catalysts.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xjt1emtL0%253D&md5=6dc5339d021a958f00c3a8af1de885a6
    9. 9
      Yang, X. F.; Wang, A.; Qiao, B.; Li, J.; Liu, J.; Zhang, T. Single-Atom Catalysts: A New Frontier in Heterogeneous Catalysis. Acc. Chem. Res. 2013, 46, 1740– 1748,  DOI: 10.1021/ar300361m
      9
      Single-Atom Catalysts: A New Frontier in Heterogeneous Catalysis
      Yang, Xiao-Feng; Wang, Aiqin; Qiao, Botao; Li, Jun; Liu, Jingyue; Zhang, Tao
      Accounts of Chemical Research (2013), 46 (8), 1740-1748CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)
      A review; supported metal nanostructures are the most widely used type of heterogeneous catalyst in industrial processes. The size of metal particles is a key factor in detg. the performance of such catalysts. In particular, because low-coordinated metal atoms often function as the catalytically active sites, the specific activity per metal atom usually increases with decreasing size of the metal particles. However, the surface free energy of metals increases significantly with decreasing particle size, promoting aggregation of small clusters. Using an appropriate support material that strongly interacts with the metal species prevents this aggregation, creating stable, finely dispersed metal clusters with a high catalytic activity, an approach industry has used for a long time. Nevertheless, practical supported metal catalysts are inhomogeneous and usually consist of a mixt. of sizes from nanoparticles to subnanometer clusters. Such heterogeneity not only reduces the metal atom efficiency but also frequently leads to undesired side reactions. It also makes it extremely difficult, if not impossible, to uniquely identify and control the active sites of interest. The ultimate small-size limit for metal particles is the single-atom catalyst (SAC), which contains isolated metal atoms singly dispersed on supports. SACs maximize the efficiency of metal atom use, which is particularly important for supported noble metal catalysts. Moreover, with well-defined and uniform single-atom dispersion, SACs offer great potential for achieving high activity and selectivity. In this Account, we highlight recent advances in prepn., characterization, and catalytic performance of SACs, with a focus on single atoms anchored to metal oxides, metal surfaces, and graphene. We discuss exptl. and theor. studies for a variety of reactions, including oxidn., water gas shift, and hydrogenation. We describe advances in understanding the spatial arrangements and electronic properties of single atoms, as well as their interactions with the support. Single metal atoms on support surfaces provide a unique opportunity to tune active sites and optimize the activity, selectivity, and stability of heterogeneous catalysts, offering the potential for applications in a variety of industrial chem. reactions.
      >> More from SciFinder ®
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    10. 10
      Grützmacher, H. Cooperating Ligands in Catalysis. Angew. Chem., Int. Ed. 2008, 47, 1814– 1818,  DOI: 10.1002/anie.200704654
      10
      Cooperating ligands in catalysis
      Gruetzmacher, Hansjoerg
      Angewandte Chemie, International Edition (2008), 47 (10), 1814-1818CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A review. Cooperating ligands participate directly in bond activation and thereby undergo a reversible chem. transformation. The interplay between metal center and ligand may facilitate a chem. process. In transition-metal-catalyzed reactions, this concept allows the discovery of new chem. reactions, such as the dehydrogenative coupling of primary alcs. and primary amines to amides and mol. hydrogen.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXjtFWhsbs%253D&md5=68febf5124b62a872928c662cd614651
    11. 11
      Boyer, J. L.; Rochford, J.; Tsai, M. K.; Muckerman, J. T.; Fujita, E. Ruthenium Complexes with Non-Innocent Ligands: Electron Distribution and Implications for Catalysis. Coord. Chem. Rev. 2010, 254, 309– 330,  DOI: 10.1016/j.ccr.2009.09.006
      11
      Ruthenium complexes with non-innocent ligands: Electron distribution and implications for catalysis
      Boyer, Julie L.; Rochford, Jonathan; Tsai, Ming-Kang; Muckerman, James T.; Fujita, Etsuko
      Coordination Chemistry Reviews (2010), 254 (3-4), 309-330CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)
      A review; ruthenium complexes with the non-innocent ligands (NILs) benzoquinone, iminobenzoquinone and benzoquinonediimine and their redox derivs. exhibit intriguing electronic properties. With the proper ligand set the NIL π* orbitals mix extensively with the ruthenium dπ orbitals resulting in delocalized electron distributions and non-integer oxidn. states, and in most of these systems a particular ruthenium oxidn. state dominates. This review critically examines the electronic structure of Ru-NIL systems from both an exptl. and computational (DFT) perspective. The electron distribution within these complexes can be modulated by altering both the ancillary ligands and the NIL, and in a few cases the resultant electron distributions are exploited for catalysis. The Ru-NIL systems that perform alc. oxidn. and water oxidn. catalysis are discussed in detail. The Tanaka catalyst, an anthracene-bridged dinuclear Ru complex, is an intriguing example of a Ru-NIL framework in catalysis. Unlike other known ruthenium water oxidn. catalysts, the two Ru atoms remain low valent during the catalytic cycle according to DFT calcns., some exptl. evidence, and predictions based on the behavior of the related mononuclear species.
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    12. 12
      Cargnello, M.; Jaén, J. D.; Garrido, J. H.; Bakhmutsky, K.; Montini, T.; Gámez, J. C.; Gorte, R.; Fornasiero, P. Exceptional Activity for Methane Combustion over Modular Pd@CeO2 Subunits on Functionalized Al2O3. Science 2012, 337, 713– 717,  DOI: 10.1126/science.1222887
      12
      Exceptional Activity for Methane Combustion over Modular Pd@CeO2 Subunits on Functionalized Al2O3
      Cargnello, M.; Jaen, J. J. Delgado; Garrido, J. C. Hernandez; Bakhmutsky, K.; Montini, T.; Gamez, J. J. Calvino; Gorte, R. J.; Fornasiero, P.
      Science (Washington, DC, United States) (2012), 337 (6095), 713-717CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
      There is a crit. need for improved methane-oxidn. catalysts to both reduce emissions of methane, a greenhouse gas, and improve the performance of gas turbines. However, materials that are currently available either have low activity below 400°C or are unstable at higher temps. Here, we describe a supramol. approach in which single units composed of a palladium (Pd) core and a ceria (CeO2) shell are preorganized in soln. and then homogeneously deposited onto a modified hydrophobic alumina. Electron microscopy and other structural methods revealed that the Pd cores remained isolated even after heating the catalyst to 850°C. Enhanced metal-support interactions led to exceptionally high methane oxidn., with complete conversion below 400°C and outstanding thermal stability under demanding conditions.
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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtFCktLbN&md5=738e9df32891d817a6120322358e5207
    13. 13
      Bruix, A.; Rodriguez, J. A.; Ramírez, P. J.; Senanayake, S. D.; Evans, J.; Park, J. B.; Stacchiola, D.; Liu, P.; Hrbek, J.; Illas, F. A New Type of Strong Metal–Support Interaction and the Production of H2 through the Transformation of Water on Pt/CeO2(111) and Pt/CeOx/TiO2(110) Catalysts. J. Am. Chem. Soc. 2012, 134, 8968– 8974,  DOI: 10.1021/ja302070k
      13
      A New Type of Strong Metal-Support Interaction and the Production of H2 through the Transformation of Water on Pt/CeO2(111) and Pt/CeOx/TiO2(110) Catalysts
      Bruix, Albert; Rodriguez, Jose A.; Ramirez, Pedro J.; Senanayake, Sanjaya D.; Evans, Jaime; Park, Joon B.; Stacchiola, Dario; Liu, Ping; Hrbek, Jan; Illas, Francesc
      Journal of the American Chemical Society (2012), 134 (21), 8968-8974CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      The electronic properties of Pt nanoparticles deposited on CeO2(111) and CeOx/TiO2(110) model catalysts have been examd. using valence photoemission expts. and d. functional theory (DFT) calcns. The valence photoemission and DFT results point to a new type of "strong metal-support interaction" that produces large electronic perturbations for small Pt particles in contact with ceria and significantly enhances the ability of the admetal to dissoc. the O-H bonds in water. When going from Pt(111) to Pt8/CeO2(111), the dissocn. of water becomes a very exothermic process. The ceria-supported Pt8 appears as a fluxional system that can change geometry and charge distribution to accommodate adsorbates better. In comparison with other water-gas shift (WGS) catalysts [Cu(111), Pt(111), Cu/CeO2(111), and Au/CeO2(111)], the Pt/CeO2(111) surface has the unique property that the admetal is able to dissoc. water in an efficient way. Furthermore, for the codeposition of Pt and CeOx nanoparticles on TiO2(110), we have found a transfer of O from the ceria to Pt that opens new paths for the WGS process and makes the mixed-metal oxide an extremely active catalyst for the prodn. of hydrogen.
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    14. 14
      Su, Y. Q.; Liu, J. X.; Filot, I. A. W.; Hensen, E. J. M. Theoretical Study of Ripening Mechanisms of Pd Clusters on Ceria. Chem. Mater. 2017, 29, 9456– 9462,  DOI: 10.1021/acs.chemmater.7b03555
      14
      Ostwald ripening mechanisms of Pd clusters on ceria
      Su, Ya-Qiong; Liu, Jin-Xun; Filot, Ivo A. W.; Hensen, Emiel J. M.
      Chemistry of Materials (2017), 29 (21), 9456-9462CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      We carried out d. functional theory calcns. to investigate the ripening of Pd clusters on CeO2(111). Starting from stable Pdn clusters (n = 1-21), we compared how these clusters can grow through Ostwald ripening and coalescence. As Pd atoms have mobility higher than that of Pdn clusters on the CeO2(111) surface, Ostwald ripening is predicted to be the dominant sintering mechanism. Particle coalescence is possible only for clusters with less than 5 Pd atoms. These ripening mechanisms are facilitated by adsorbed CO through lowering barriers for the cluster diffusion, detachment of a Pd atom from clusters, and transformation of initial planar clusters.
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    15. 15
      Negreiros, F. R.; Fabris, S. Role of Cluster Morphology in the Dynamics and Reactivity of Subnanometer Pt Clusters Supported on Ceria Surfaces. J. Phys. Chem. C 2014, 118, 21014– 21020,  DOI: 10.1021/jp506404z
      15
      Role of Cluster Morphology in the Dynamics and Reactivity of Subnanometer Pt Clusters Supported on Ceria Surfaces
      Negreiros, Fabio R.; Fabris, Stefano
      Journal of Physical Chemistry C (2014), 118 (36), 21014-21020CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      Subnanometer (sub-nm) Pt clusters supported by highly reducible oxide surfaces were studied, and the role of cluster morphol. in the thermodn. and kinetics of surface processes relevant for reactivity, namely cluster mobility, reverse oxygen spillover, and oxygen vacancy formation, was elucidated. The relationships between cluster morphol. and reactivity are rarely considered in computational studies because of the large domain and complexity of the potential energy surface, particularly in the presence of strong metal-support interaction. Global optimization algorithms together with Hubbard-cor. d. functional theory calcns. (DFT + U) are used to identify the stable and metastable morphologies of Pt3-Pt6 clusters supported on pristine and defective CeO2(111) surfaces. This systematic exploration for these sub-nm Pt particles shows that the charge of the supported cluster, its bonding to the substrate, and the degree of ceria redn. depend on the metal/oxide interface area and on the cluster morphol. Concerning reaction thermodn. and kinetics, the use of global optimization methods leads to very different results as compared to usual minimization procedures. By allowing for morphol. changes during reaction, the energetics of reverse O spillover changes from highly endothermic to exothermic and leads to new min.-energy reaction and diffusion mechanisms. The diffusion kinetics predicts clusters as small as Pt6 to be resistant to sintering on ceria surfaces. The relevance of these findings for larger metal clusters and for supporting oxide nanoparticles is discussed as well as their connection with the recent literature.
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    16. 16
      Hansen, T. W.; DeLaRiva, A. T.; Challa, S. R.; Datye, A. K. Sintering of Catalytic Nanoparticles: Particle Migration or Ostwald Ripening?. Acc. Chem. Res. 2013, 46, 1720– 1730,  DOI: 10.1021/ar3002427
      16
      Sintering of Catalytic Nanoparticles: Particle Migration or Ostwald Ripening?
      Hansen, Thomas W.; De La Riva, Andrew T.; Challa, Sivakumar R.; Datye, Abhaya K.
      Accounts of Chemical Research (2013), 46 (8), 1720-1730CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)
      A review; metal nanoparticles contain the active sites in heterogeneous catalysts, which are important for many industrial applications including the prodn. of clean fuels, chems. and pharmaceuticals, and the cleanup of exhaust from automobiles and stationary power plants. Sintering, or thermal deactivation, is an important mechanism for the loss of catalyst activity. This is esp. true for high temp. catalytic processes, such as steam reforming, automotive exhaust treatment, or catalytic combustion. With dwindling supplies of precious metals and increasing demand, fundamental understanding of catalyst sintering is very important for achieving clean energy and a clean environment, and for efficient chem. conversion processes with atom selectivity. Scientists have proposed two mechanisms for sintering of nanoparticles: particle migration and coalescence (PMC) and Ostwald ripening (OR). PMC involves the mobility of particles in a Brownian-like motion on the support surface, with subsequent coalescence leading to nanoparticle growth. In contrast, OR involves the migration of adatoms or mobile mol. species, driven by differences in free energy and local adatom concns. on the support surface. In this Account, we divide the process of sintering into three phases. Phase I involves rapid loss in catalyst activity (or surface area), phase II is where sintering slows down, and phase III is where the catalyst may reach a stable performance. Much of the previous work is based on inferences from catalysts that were obsd. before and after long term treatments. While the general phenomena can be captured correctly, the mechanisms cannot be detd. Advancements in the techniques of in situ TEM allow us to observe catalysts at elevated temps. under working conditions. We review recent evidence obtained via in situ methods to det. the relative importance of PMC and OR in each of these phases of catalyst sintering. The evidence suggests that, in phase I, OR is responsible for the rapid loss of activity that occurs when particles are very small. Surprisingly, very little PMC is obsd. in this phase. Instead, the rapid loss of activity is caused by the disappearance of the smallest particles. These findings are in good agreement with representative atomistic simulations of sintering. In phase II, sintering slows down since the smallest particles have disappeared. We now see a combination of PMC and OR, but do not fully understand the relative contribution of each of these processes to the overall rates of sintering. In phase III, the particles have grown large and other parasitic phenomena, such as support restructuring, can become important, esp. at high temps. Examg. the evolution of particle size and surface area with time, we do not see a stable or equil. state, esp. for catalysts operating at elevated temps. In conclusion, the recent literature, esp. on in situ studies, shows that OR is the dominant process causing the growth of nanoparticle size. Consequently, this leads to the loss of surface area and activity. While particle migration could be controlled through suitable structuring of catalyst supports, it is more difficult to control the mobility of atomically dispersed species. These insights into the mechanisms of sintering could help to develop sinter-resistant catalysts, with the ultimate goal of designing catalysts that are self-healing.
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    17. 17
      Wang, C.; Gu, X. K.; Yan, H.; Lin, Y.; Li, J.; Liu, D.; Li, W. X.; Lu, J. Water-Mediated Mars–Van Krevelen Mechanism for CO Oxidation on Ceria-Supported Single-Atom Pt Catalyst. ACS Catal. 2017, 7, 887– 891,  DOI: 10.1021/acscatal.6b02685
      17
      Water-Mediated Mars-Van Krevelen Mechanism for CO Oxidation on Ceria-Supported Single-Atom Pt1 Catalyst
      Wang, Chunlei; Gu, Xiang-Kui; Yan, Huan; Lin, Yue; Li, Junjie; Liu, Dandan; Li, Wei-Xue; Lu, Junling
      ACS Catalysis (2017), 7 (1), 887-891CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
      In water-promoted CO oxidn., water was thought not to directly participate in CO2 prodn. Here we report that via a water-mediated Mars-van Krevelen (MvK) mechanism, water can directly contribute to about 50% of CO2 prodn. on a single-atom Pt1/CeO2 catalyst. The origin is the facile reaction of CO with the hydroxyl from dissocd. water to yield the carboxyl intermediate, which dehydrogenates subsequently with the help of a lattice hydroxyl to generate CO2 and water. The water-mediated MvK type reaction found here provides new insights in the promotion role of water in heterogeneous catalysis.
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    18. 18
      Jones, J.; Xiong, H.; DeLaRiva, A. T.; Peterson, E. J.; Pham, H.; Challa, S. R.; Qi, G.; Oh, S.; Wiebenga, M. H.; Hernández, X. I. P. Thermally Stable Single-AtomPlatinum-on-Ceria Catalysts via Atom Trapping. Science 2016, 353, 150– 154,  DOI: 10.1126/science.aaf8800
      18
      Thermally stable single-atom platinum-on-ceria catalysts via atom trapping
      Jones, John; Xiong, Haifeng; De La Riva, Andrew T.; Peterson, Eric J.; Pham, Hien; Challa, Sivakumar R.; Qi, Gongshin; Oh, Se; Wiebenga, Michelle H.; Pereira Hernandez, Xavier Isidro; Wang, Yong; Datye, Abhaya K.
      Science (Washington, DC, United States) (2016), 353 (6295), 150-154CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
      Catalysts based on single atoms of scarce precious metals can lead to more efficient use through enhanced reactivity and selectivity. However, single atoms on catalyst supports can be mobile and aggregate into nanoparticles when heated at elevated temps. High temps. are detrimental to catalyst performance unless these mobile atoms can be trapped. We used ceria powders having similar surface areas but different exposed surface facets. When mixed with a platinum/aluminum oxide catalyst and aged in air at 800°C, the platinum transferred to the ceria and was trapped. Polyhedral ceria and nanorods were more effective than ceria cubes at anchoring the platinum. Performing synthesis at high temps. ensures that only the most stable binding sites are occupied, yielding a sinter-resistant, atomically dispersed catalyst.
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    19. 19
      Bruix, A.; Lykhach, Y.; Matolínová, I.; Neitzel, A.; Skála, T.; Tsud, N.; Vorokhta, M.; Stetsovych, V.; Ševčíková, K.; Mysliveček, J. Maximum Noble Metal Efficiency in Catalytic Materials: Atomically Dispersed Surface Platinum. Angew. Chem., Int. Ed. 2014, 53, 10525– 10530,  DOI: 10.1002/anie.201402342
      There is no corresponding record for this reference.
    20. 20
      Liu, J. C.; Wang, Y. G.; Li, J. Toward Rational Design of Oxide-Supported Single-Atom Catalysts: Atomic Dispersion of Gold on Ceria. J. Am. Chem. Soc. 2017, 139, 6190– 6199,  DOI: 10.1021/jacs.7b01602
      20
      Toward Rational Design of Oxide-Supported Single-Atom Catalysts: Atomic Dispersion of Gold on Ceria
      Liu, Jin-Cheng; Wang, Yang-Gang; Li, Jun
      Journal of the American Chemical Society (2017), 139 (17), 6190-6199CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      We have constructed a general thermodn. model of chem. potentials and applied ab initio electronic structure and mol. dynamics simulations, as well as kinetic Monte Carlo anal., to probe the dynamical, reactive, and kinetic aspects of metal single-atom catalysts (SACs) on oxide support. We choose Au single atoms (SAs) supported on ceria as a typical example to demonstrate how our model can guide the rational design of highly stable and reactive SACs. It is shown that, under realistic conditions, various factors such as temp., pressure, particle size, and the reducibility of the support can strongly affect both the stability and the reactivity of SACs by altering the relative chem. potentials between SAs and metal nanoparticles (NPs). The Au SAs at step sites of ceria support are rather stable, even at temps. as high as 700 K, and exhibit around 10 orders of magnitude more reactivity for CO oxidn. than the terrace sites. Remarkably, under reaction conditions, Au SAs can be dynamically created at the interface of small-size Au NPs on ceria support even without step sites, which accounts for the puzzling significant size effect in gold catalysis. Our work underscores an unrecognized crit. role of Au SAs in gold nanocatalysis and provides a general methodol. for designing the metal SACs on oxide supports.
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    21. 21
      Ouyang, R.; Liu, J. X.; Li, W. X. Atomistic Theory of Ostwald Ripening and Disintegration of Supported Metal Particles under Reaction Conditions. J. Am. Chem. Soc. 2013, 135, 1760– 1771,  DOI: 10.1021/ja3087054
      21
      Atomistic Theory of Ostwald Ripening and Disintegration of Supported Metal Particles under Reaction Conditions
      Ouyang, Runhai; Liu, Jin-Xun; Li, Wei-Xue
      Journal of the American Chemical Society (2013), 135 (5), 1760-1771CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Understanding Ostwald ripening and disintegration of supported metal particles under operating conditions has been of central importance in the study of sintering and dispersion of heterogeneous catalysts for long-term industrial implementation. To achieve a quant. description of these complicated processes, an atomistic and generic theory taking into account the reaction environment, particle size and morphol., and metal-support interaction is developed. It includes (1) energetics of supported metal particles, (2) formation of monomers (both the metal adatoms and metal-reactant complexes) on supports, and (3) corresponding sintering rate equations and total activation energies, in the presence of reactants at arbitrary temp. and pressure. The thermodn. criteria for the reactant assisted Ostwald ripening and induced disintegration are formulated, and the influence of reactants on sintering kinetics and redispersion are mapped out. Most energetics and kinetics barriers in the theory can be obtained conveniently by first-principles theory calcns. This allows for the rapid exploration of sintering and disintegration of supported metal particles in huge phase space of structures and compns. under various reaction environments. General strategies of suppressing the sintering of the supported metal particles and facilitating the redispersions of the low surface area catalysts are proposed. The theory is applied to TiO2(110) supported Rh particles in the presence of carbon monoxide, and reproduces well the broad temp., pressure, and particle size range over which the sintering and redispersion occurred in such expts. The result also highlights the importance of the metal-carbonyl complexes as monomers for Ostwald ripening and disintegration of supported metal catalysts in the presence of CO.
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    22. 22
      Berkó, A.; Solymosi, F. Adsorption-Induced Structural Changes of Rh Supported by TiO2(110)-(1× 2): an STM Study. J. Catal. 1999, 183, 91– 101,  DOI: 10.1006/jcat.1998.2368
      There is no corresponding record for this reference.
    23. 23
      Goldsmith, B. R.; Sanderson, E. D.; Ouyang, R.; Li, W. X. CO-and NO-Induced Disintegration and Redispersion of Three-Way Catalysts Rhodium, Palladium, and Platinum: An ab Initio Thermodynamics Study. J. Phys. Chem. C 2014, 118, 9588– 9597,  DOI: 10.1021/jp502201f
      23
      CO- and NO-Induced Disintegration and Redispersion of Three-Way Catalysts Rhodium, Palladium, and Platinum: An ab Initio Thermodynamics Study
      Goldsmith, Bryan R.; Sanderson, Evan D.; Ouyang, Runhai; Li, Wei-Xue
      Journal of Physical Chemistry C (2014), 118 (18), 9588-9597CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      Disintegration of supported nanoparticles (NPs) in the presence of reactants can lead to catalyst deactivation or be exploited to redisperse sintered catalysts. To better understand the stability of TiO2(110)-supported three-way catalysts Rh, Pd, and Pt NPs during NOx and CO redn., we present an ab initio thermodn. study of the feasibility for these NPs to disintegrate into adatom-reactant complexes across a large parameter space of temps., pressures, and sizes. The tendencies for disintegration and redispersion between supported Rh, Pd, and Pt NPs are established. Compared to both Pd and Pt, Rh NPs are found to be more susceptible to either NO- or CO-induced disintegration, due to the large and exothermic formation energy of the Rh adatom complexes. Moreover, NO is a more efficient reactant for particle redispersion than CO. These findings provide valuable insights for how to either prevent reactant-induced NP disintegration or facilitate reactant-induced redispersion of sintered catalysts.
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    24. 24
      Suzuki, A.; Inada, Y.; Yamaguchi, A.; Chihara, T.; Yuasa, M.; Nomura, M.; Iwasawa, Y. Time Scale and Elementary Steps of CO-Induced Disintegration of Surface Rhodium Clusters. Angew. Chem., Int. Ed. 2003, 42, 4795– 4799,  DOI: 10.1002/anie.200352318
      24
      Time scale and elementary steps of CO-induced disintegration of surface rhodium clusters
      Suzuki, Akane; Inada, Yasuhiro; Yamaguchi, Aritomo; Chihara, Teiji; Yuasa, Makoto; Nomura, Masaharu; Iwasawa, Yasuhiro
      Angewandte Chemie, International Edition (2003), 42 (39), 4795-4799CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      While the reaction kinetics and dynamics of mols. adsorbed on catalyst surfaces have been extensively studied, little is known about the dynamic structural change of active metal sites in supported metal cluster/nanoparticle catalysts, such as the time scale of formation and disintegration of the active structure induced by reaction gases and the sequence of bond rearrangements involved in the dynamic event on the surfaces. The in situ time-resolved structural characterization of surface metal clusters and nanoparticles by energy-dispersive x-ray absorption fine structure (DXAFS) is essential to document their dynamic property on an at. basis, which has been a long-term challenge to be addressed. We have succeeded in observing the CO-induced disintegration process of Rh clusters on an Al2O3 surface by DXAFS every 100 ms. Previous static studies on the similar surface phenomenon have been performed by IR, XAFS, and STM, which revealed the structural modification of highly dispersed Rh nanoparticles/Al2O3 catalysts that leads to the formation of isolated Rh(CO)2 species by CO adsorption. The DXAFS technique has been developed and improved to provide in situ structural information on dispersed catalytic materials at a time resoln. of 1 s-several 10 s. Herein, we report novel issues found by the time-resolved DXAFS characterization of the structural disintegrity of Rh clusters on an Al2O3 surface, namely, the time scale and sequence of dynamic bond rearrangements in the clusters and at the interface.
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    25. 25
      Berko, A.; Szökő, J.; Solymosi, F. Effect of CO on the Morphology of Pt Nanoparticles Supported on TiO2(110)-(1× n).. Surf. Sci. 2004, 566, 337– 342,  DOI: 10.1016/j.susc.2004.05.065
      There is no corresponding record for this reference.
    26. 26
      Stamatakis, M.; Vlachos, D. G. A Graph-Theoretical Kinetic Monte Carlo Framework for on-Lattice Chemical Kinetics. J. Chem. Phys. 2011, 134, 214115,  DOI: 10.1063/1.3596751
      26
      A graph-theoretical kinetic Monte Carlo framework for on-lattice chemical kinetics
      Stamatakis, Michail; Vlachos, Dionisios G.
      Journal of Chemical Physics (2011), 134 (21), 214115/1-214115/13CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
      Existing kinetic Monte Carlo (KMC) frameworks for the simulation of adsorption, desorption, diffusion, and reaction on a lattice often assume that each participating species occupies a single site and represent elementary events involving a max. of two sites. However, these assumptions may be inadequate, esp. in the case of complex chemistries, involving multidentate species or complex coverage and neighboring patterns between several lattice sites. We have developed a novel approach that employs graph-theor. ideas to overcome these challenges and treat easily complex chemistries. As a benchmark, the Ziff-Gulari-Barshad system is simulated and comparisons of the computational times of the graph-theor. KMC and a simpler KMC approach are made. Further, to demonstrate the capabilities of our framework, the water-gas shift chem. on Pt(111) is simulated. (c) 2011 American Institute of Physics.
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    27. 27
      Kresse, G.; Hafner, J. Ab initio Molecular-Dynamics Simulation of the Liquid-Metal–Amorphous-Semiconductor Transition in Germanium. Phys. Rev. B: Condens. Matter Mater. Phys. 1994, 49, 14251,  DOI: 10.1103/PhysRevB.49.14251
      27
      Ab initio molecular-dynamics simulation of the liquid-metal-amorphous-semiconductor transition in germanium
      Kresse, G.; Hafner, J.
      Physical Review B: Condensed Matter and Materials Physics (1994), 49 (20), 14251-69CODEN: PRBMDO; ISSN:0163-1829.
      The authors present ab initio quantum-mech. mol.-dynamics simulations of the liq.-metal-amorphous-semiconductor transition in Ge. The simulations are based on (a) finite-temp. d.-functional theory of the 1-electron states, (b) exact energy minimization and hence calcn. of the exact Hellmann-Feynman forces after each mol.-dynamics step using preconditioned conjugate-gradient techniques, (c) accurate nonlocal pseudopotentials, and (d) Nose' dynamics for generating a canonical ensemble. This method gives perfect control of the adiabaticity of the electron-ion ensemble and allows the authors to perform simulations over >30 ps. The computer-generated ensemble describes the structural, dynamic, and electronic properties of liq. and amorphous Ge in very good agreement with expt.. The simulation allows the authors to study in detail the changes in the structure-property relation through the metal-semiconductor transition. The authors report a detailed anal. of the local structural properties and their changes induced by an annealing process. The geometrical, bounding, and spectral properties of defects in the disordered tetrahedral network are studied and compared with expt.
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    28. 28
      Blöchl, P. E. Projector Augmented-Wave Method. Phys. Rev. B: Condens. Matter Mater. Phys. 1994, 50, 17953,  DOI: 10.1103/PhysRevB.50.17953
      28
      Projector augmented-wave method
      Blochl
      Physical review. B, Condensed matter (1994), 50 (24), 17953-17979 ISSN:0163-1829.
      There is no expanded citation for this reference.
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    29. 29
      Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation mMade Simple. Phys. Rev. Lett. 1996, 77, 3865,  DOI: 10.1103/PhysRevLett.77.3865
      There is no corresponding record for this reference.
    30. 30
      Dudarev, S.; Botton, G.; Savrasov, S.; Humphreys, C.; Sutton, A. Electron-Energy-Loss Spectra and the Structural Stability of Nickel Oxide: An LSDA+ U study. Phys. Rev. B: Condens. Matter Mater. Phys. 1998, 57, 1505,  DOI: 10.1103/PhysRevB.57.1505
      30
      Electron-energy-loss spectra and the structural stability of nickel oxide: An LSDA+U study
      Dudarev, S. L.; Botton, G. A.; Savrasov, S. Y.; Humphreys, C. J.; Sutton, A. P.
      Physical Review B: Condensed Matter and Materials Physics (1998), 57 (3), 1505-1509CODEN: PRBMDO; ISSN:0163-1829. (American Physical Society)
      By taking better account of electron correlations in the 3d shell of metal ions in Ni oxide it is possible to improve the description of both electron energy loss spectra and parameters characterizing the structural stability of the material compared with local spin d. functional theory.
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    31. 31
      Fabris, S.; de Gironcoli, S.; Baroni, S.; Vicario, G.; Balducci, G. Reply to “Comment on ‘Taming Multiple Valency with Density Functionals: A Case Study of Defective Ceria’. Phys. Rev. B: Condens. Matter Mater. Phys. 2005, 72, 237102,  DOI: 10.1103/PhysRevB.72.237102
      31
      Reply to "Comment on 'Taming multiple valency with density functionals: A case study of defective ceria' "
      Fabris, Stefano; de Gironcoli, Stefano; Baroni, Stefano; Vicario, Gianpaolo; Balducci, Gabriele
      Physical Review B: Condensed Matter and Materials Physics (2005), 72 (23), 237102/1-237102/2CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
      A polemic in reply to G. Kresse and P. Blaha, ibid, 237101. We address the issues raised in the preceding Comment by discussing the effects of an explicit account of the nonlinear core correction (NLCC) into the Ce pseudopotential employed in our previous calcns. of reduced ceria [Phys. Rev. B 71, 041102(R) (2005)]. At the plain d.-functional-theory (DFT) level, such an account brings our pseudopotential results in good agreement with all-electron ones, which do not predict the insulating character of reduced ceria. At the DFT+U level, the inclusion of the NLCC has no effect on the previously reported electronic structure and equil. geometries. The dependency of the DFT+U energy on the choice of the projector functions defining the Hubbard-U functional is discussed in further detail.
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    32. 32
      Cococcioni, M.; De Gironcoli, S. Linear Response Approach to the Calculation of the Effective Interaction Parameters in the LDA+ U Method. Phys. Rev. B: Condens. Matter Mater. Phys. 2005, 71, 035105,  DOI: 10.1103/PhysRevB.71.035105
      32
      Linear response approach to the calculation of the effective interaction parameters in the LDA+U method
      Cococcioni, Matteo; de Gironcoli, Stefano
      Physical Review B: Condensed Matter and Materials Physics (2005), 71 (3), 035105/1-035105/16CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
      We reexamine the LDA + U method of Anisimov and co-workers in the framework of a plane-wave pseudopotential approach. A simplified rotational-invariant formulation is adopted. The calcn. of the Hubbard U entering the expression of the functional is discussed and a linear response approach is proposed that is internally consistent with the chosen definition for the occupation matrix of the relevant localized orbitals. In this way we obtain a scheme whose functionality should not depend strongly on the particular implementation of the model in ab initio calcns. We demonstrate the accuracy of the method, computing structural and electronic properties of a few systems including transition and rare-earth correlated metals, transition metal monoxides, and iron silicate.
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    33. 33
      Castleton, C.; Kullgren, J.; Hermansson, K. Tuning LDA+ U for Electron Localization and Structure at Oxygen Vacancies in Ceria. J. Chem. Phys. 2007, 127, 244704,  DOI: 10.1063/1.2800015
      33
      Tuning LDA + U for electron localization and structure at oxygen vacancies in ceria
      Castleton, C. W. M.; Kullgren, J.; Hermansson, K.
      Journal of Chemical Physics (2007), 127 (24), 244704/1-244704/11CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
      We examine the real space structure and the electronic structure (particularly Ce4f electron localization) of oxygen vacancies in CeO2 (ceria) as a function of U in d. functional theory studies with the rotationally invariant forms of the LDA + U and GGA + U functionals. The four nearest neighbor Ce ions always relax outwards, with those not carrying localized Ce4f charge moving furthest. Several quantification schemes show that the charge starts to become localized at U ≈ 3 eV and that the degree of localization reaches a max. at ∼6 eV for LDA + U or at ∼5.5 eV for GGA + U. For higher U it decreases rapidly as charge is transferred onto second neighbor O ions and beyond. The localization is never into at. corelike states; at max. localization about 80-90% of the Ce4f charge is located on the two nearest neighboring Ce ions. However, if we look at the total at. charge we find that the two ions only make a net gain of (0.2-0.4)e each, so localization is actually very incomplete, with localization of Ce4f electrons coming at the expense of moving other electrons off the Ce ions. We have also revisited some properties of defect-free ceria and find that with LDA + U the crystal structure is actually best described with U = 3-4 eV, while the exptl. band structure is obtained with U = 7-8 eV. (For GGA + U the lattice parameters worsen for U > 0 eV, but the band structure is similar to LDA + U.) The best overall choice is U ≈ 6 eV with LDA + U and ≈5.5 eV for GGA + U, since the localization is most important, but a consistent choice for both CeO2 and Ce2O3, with and without vacancies, is hard to find.
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    34. 34
      Da Silva, J. L.; Ganduglia-Pirovano, M. V.; Sauer, J.; Bayer, V.; Kresse, G. Hybrid Functionals Ppplied to Rare-Earth Oxides: The Example of Ceria. Phys. Rev. B: Condens. Matter Mater. Phys. 2007, 75, 045121,  DOI: 10.1103/PhysRevB.75.045121
      There is no corresponding record for this reference.
    35. 35
      Henkelman, G.; Jónsson, H. Improved Tangent Estimate in the Nudged Elastic Band Method for Finding Minimum Energy Paths and Saddle Points. J. Chem. Phys. 2000, 113, 9978– 9985,  DOI: 10.1063/1.1323224
      35
      Improved tangent estimate in the nudged elastic band method for finding minimum energy paths and saddle points
      Henkelman, Graeme; Jonsson, Hannes
      Journal of Chemical Physics (2000), 113 (22), 9978-9985CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
      An improved way of estg. the local tangent in the nudged elastic band method for finding min. energy paths is presented. In systems where the force along the min. energy path is large compared to the restoring force perpendicular to the path and when many images of the system are included in the elastic band, kinks can develop and prevent the band from converging to the min. energy path. We show how the kinks arise and present an improved way of estg. the local tangent which solves the problem. The task of finding an accurate energy and configuration for the saddle point is also discussed and examples given where a complementary method, the dimer method, is used to efficiently converge to the saddle point. Both methods only require the first deriv. of the energy and can, therefore, easily be applied in plane wave based d.-functional theory calcns. Examples are given from studies of the exchange diffusion mechanism in a Si crystal, Al addimer formation on the Al(100) surface, and dissociative adsorption of CH4 on an Ir(111) surface.
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    36. 36
      Sheppard, D.; Terrell, R.; Henkelman, G. Optimization Methods for Finding Minimum Energy Paths. J. Chem. Phys. 2008, 128, 134106,  DOI: 10.1063/1.2841941
      36
      Optimization methods for finding minimum energy paths
      Sheppard, Daniel; Terrell, Rye; Henkelman, Graeme
      Journal of Chemical Physics (2008), 128 (13), 134106/1-134106/10CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
      A comparison of chain-of-states based methods for finding min. energy pathways (MEPs) is presented. In each method, a set of images along an initial pathway between two local min. is relaxed to find a MEP. We compare the nudged elastic band (NEB), doubly nudged elastic band, string, and simplified string methods, each with a set of commonly used optimizers. Our results show that the NEB and string methods are essentially equiv. and the most efficient methods for finding MEPs when coupled with a suitable optimizer. The most efficient optimizer was found to be a form of the limited-memory Broyden-Fletcher-Goldfarb-Shanno method in which the approx. inverse Hessian is constructed globally for all images along the path. The use of a climbing-image allows for finding the saddle point while representing the MEP with as few images as possible. If a highly accurate MEP is desired, it is found to be more efficient to descend from the saddle to the min. than to use a chain-of-states method with many images. Our results are based on a pairwise Morse potential to model rearrangements of a heptamer island on Pt(111), and plane-wave based d. functional theory to model a rollover diffusion mechanism of a Pd tetramer on MgO(100) and dissociative adsorption and diffusion of oxygen on Au(111). (c) 2008 American Institute of Physics.
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    37. 37
      Stamatakis, M. Zacros: Advanced Lattice-KMC Simulation Made Easy; http://www.e-lucid.com/i/software/material_modelling/Zacros.html.
      There is no corresponding record for this reference.
    38. 38
      Reuter, K.; Scheffler, M. First-Principles Kinetic Monte Carlo Simulations for Heterogeneous Catalysis: Application to the CO Oxidation at RuO2(110). Phys. Rev. B: Condens. Matter Mater. Phys. 2006, 73, 045433,  DOI: 10.1103/PhysRevB.73.045433
      38
      First-principles kinetic Monte Carlo simulations for heterogeneous catalysis: Application to the CO oxidation at RuO2(110)
      Reuter, Karsten; Scheffler, Matthias
      Physical Review B: Condensed Matter and Materials Physics (2006), 73 (4), 045433/1-045433/17CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
      We describe a first-principles statistical mechanics approach enabling us to simulate the steady-state situation of heterogeneous catalysis. In a first step, d.-functional theory together with transition-state theory is employed to obtain the energetics of the relevant elementary processes. Subsequently the statistical mechanics problem is solved by the kinetic Monte Carlo method, which accounts for the correlations, fluctuations, and spatial distributions of the chems. at the surface of the catalyst under steady-state conditions. Applying this approach to the catalytic oxidn. of CO at RuO2(110), we det. the surface at. structure and compn. in reactive environments ranging from ultra-high vacuum (UHV) to technol. relevant conditions, i.e., up to pressures of several atmospheres and elevated temps. We also compute the CO2 formation rates (turnover frequencies). The results are in quant. agreement with all existing exptl. data. We find that the high catalytic activity of this system is intimately connected with a disordered, dynamic surface "phase" with significant compositional fluctuations. In this active state the catalytic function results from a self-regulating interplay of several elementary processes.
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    39. 39
      Pineda, M.; Stamatakis, M. Beyond Mean-Field Approximations for Accurate and Computationally Efficient Models of on-Lattice Chemical Kinetics. J. Chem. Phys. 2017, 147, 024105,  DOI: 10.1063/1.4991690
      39
      Beyond mean-field approximations for accurate and computationally efficient models of on-lattice chemical kinetics
      Pineda, M.; Stamatakis, M.
      Journal of Chemical Physics (2017), 147 (2), 024105/1-024105/12CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
      Modeling the kinetics of surface catalyzed reactions is essential for the design of reactors and chem. processes. The majority of microkinetic models employ mean-field approxns., which lead to an approx. description of catalytic kinetics by assuming spatially uncorrelated adsorbates. On the other hand, kinetic Monte Carlo (KMC) methods provide a discrete-space continuous-time stochastic formulation that enables an accurate treatment of spatial correlations in the adlayer, but at a significant computation cost. In this work, we use the so-called cluster mean-field approach to develop higher order approxns. that systematically increase the accuracy of kinetic models by treating spatial correlations at a progressively higher level of detail. We further demonstrate our approach on a reduced model for NO oxidn. incorporating first nearest-neighbor lateral interactions and construct a sequence of approxns. of increasingly higher accuracy, which we compare with KMC and mean-field. The latter is found to perform rather poorly, overestimating the turnover frequency by several orders of magnitude for this system. On the other hand, our approxns., while more computationally intense than the traditional mean-field treatment, still achieve tremendous computational savings compared to KMC simulations, thereby opening the way for employing them in multiscale modeling frameworks. (c) 2017 American Institute of Physics.
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    40. 40
      Eyring, H. The Activated Complex in Chemical Reactions. J. Chem. Phys. 1935, 3, 107– 115,  DOI: 10.1063/1.1749604
      40
      Statistical Mechanical Treatment of the Activated Complex in Chemical Reactions
      Eyring, Henry
      Journal of Chemical Physics (1935), 3 (), 107-15CODEN: JCPSA6; ISSN:0021-9606.
      A possible error in Eyring's recent calcns. of abs. reaction rates due to the short life and consequent unsharp quantization of the activated complex is noted. The existence of this error is made more probable by a consideration of the target area required by Eyring's equations at low temps. There is no doubt that his treatment becomes asymptotically correct at high temps.
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    41. 41
      Piccinin, S.; Stamatakis, M. CO Oxidation on Pd (111): a First-Principles-Based Kinetic Monte Carlo Study. ACS Catal. 2014, 4, 2143– 2152,  DOI: 10.1021/cs500377j
      41
      CO Oxidation on Pd(111): A First-Principles-Based Kinetic Monte Carlo Study
      Piccinin, Simone; Stamatakis, Michail
      ACS Catalysis (2014), 4 (7), 2143-2152CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
      CO oxidn. on O-precovered Pd(111) surfaces exhibits remarkably different reactivities at different temps., which correlate with structural changes in the at. O overlayer. Stoichiometric titrn. expts. by Nakai et al. (J. Chem. Phys.2006, 124, 224712) show that although the p(2 × 2) ordered phase is inert, the (√3 × √3) and p(2 × 1) phases that form at 320 and 190 K, resp., have different apparent activation energies and reaction orders with respect to O coverage. In this work, we perform first-principles-based kinetic Monte Carlo (kMC) simulations to understand the behavior of this catalytic system and shed light on the origin of the changes in reactivity. Accounting explicitly for lateral interactions among adsorbates and for their impact on the activation energies of the elementary processes, our simulations reproduce quant. the main features of the exptl. measurements, and we show that the relative rates of CO adsorption and surface reaction are different as the temp. changes. We find that ordering of the adsorbate layer strongly depends on the strength of the lateral interactions but does not have a significant role on the catalytic properties of the system.
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    42. 42
      Peleš, S.; Munsky, B.; Khammash, M. Reduction and Solution of the Chemical Master Equation using Time Scale Separation and Finite State Projection. J. Chem. Phys. 2006, 125, 204104,  DOI: 10.1063/1.2397685
      42
      Reduction and solution of the chemical master equation using time scale separation and finite state projection
      Peles, Slaven; Munsky, Brian; Khammash, Mustafa
      Journal of Chemical Physics (2006), 125 (20), 204104/1-204104/13CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
      The dynamics of chem. reaction networks often takes place on widely differing time scales-from the order of nanoseconds to the order of several days. This is particularly true for gene regulatory networks, which are modeled by chem. kinetics. Multiple time scales in math. models often lead to serious computational difficulties, such as numerical stiffness in the case of differential equations or excessively redundant Monte Carlo simulations in the case of stochastic processes. A model redn. method is presented for study of stochastic chem. kinetic systems that takes advantage of multiple time scales. The method applies to finite projections of the chem. master equation and allows for effective time scale sepn. of the system dynamics. This method is implemented in a novel numerical algorithm that exploits the time scale sepn. to achieve model order redns. while enabling error checking and control. The efficiency is illustrated of the method in several examples motivated by recent developments in gene regulatory networks.
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    43. 43
      Stamatakis, M.; Vlachos, D. G. Unraveling the Complexity of Catalytic Reactions via Kinetic Monte Carlo simulation: Current Status and Frontiers. ACS Catal. 2012, 2, 2648– 2663,  DOI: 10.1021/cs3005709
      43
      Unraveling the Complexity of Catalytic Reactions via Kinetic Monte Carlo Simulation: Current Status and Frontiers
      Stamatakis, Michail; Vlachos, Dionisios G.
      ACS Catalysis (2012), 2 (12), 2648-2663CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
      A review; over the past two decades, the necessity for predictive models of chem. kinetics on catalytic surfaces has motivated the development of ab initio kinetic Monte Carlo (KMC) simulation frameworks. These frameworks have been successfully used to investigate chemistries of academic interest and industrial importance, such as CO oxidn., NO oxidn. and redn., ethylene hydrogenation, CO hydrogenation to ethanol, and water-gas shift. These studies have shed light on the effect of catalyst compn., surface structure, lateral interactions, and operating conditions on the apparent turnover frequency of the chemistries of interest. Yet, extending the existing KMC approaches to study large chemistries on complex catalytic structures poses several challenges. In this review, we discuss the recent milestones in the area of KMC simulation of chem. kinetics on catalytic surfaces and review a no. of studies that have furthered our fundamental understanding of specific chemistries. In addn., we provide directions for future research aiming toward incorporating detailed physics and chem., as well as assessing and improving the accuracy of KMC methods, toward developing quant. models of surface kinetics.
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    44. 44
      Stamatakis, M.; Vlachos, D. G. Equivalence of on-Lattice Stochastic Chemical Kinetics with the Well-Mixed Chemical Master Equation in the Limit of Fast Diffusion. Comput. Chem. Eng. 2011, 35, 2602– 2610,  DOI: 10.1016/j.compchemeng.2011.05.008
      44
      Equivalence of on-lattice stochastic chemical kinetics with the well-mixed chemical master equation in the limit of fast diffusion
      Stamatakis, Michail; Vlachos, Dionisios G.
      Computers & Chemical Engineering (2011), 35 (12), 2602-2610CODEN: CCENDW; ISSN:0098-1354. (Elsevier B.V.)
      Well-mixed and lattice-based descriptions of stochastic chem. kinetics were extensively used in the literature. Realizations of the corresponding stochastic processes are obtained by the D. T. Gillespie (1976, 1977) stochastic simulation algorithm and lattice kinetic Monte Carlo algorithms, resp. However, the two frameworks have remained disconnected. The equivalence is shown of these frameworks whereby the stochastic lattice kinetics reduces to effective well-mixed kinetics in the limit of fast diffusion. In the latter, the lattice structure appears implicitly, as the lumped rate of bimol. reactions depends on the no. of neighbors of a site on the lattice. Moreover, a mapping is proposed between the stochastic propensities and the deterministic rates of the well-mixed vessel and lattice dynamics that illustrates the hierarchy of models and the key parameters that enable model redn.
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    45. 45
      Boyer, L.; Broughton, J. Statics and Dynamics of Icosahedrally Twinned and Single-Crystal FCC Clusters. Phys. Rev. B: Condens. Matter Mater. Phys. 1990, 42, 11461,  DOI: 10.1103/PhysRevB.42.11461
      There is no corresponding record for this reference.
    46. 46
      Vlachos, D. G.; Schmidt, L. D.; Aris, R. Structures of Small Metal Clusters. i. Low Temperature Behavior. J. Chem. Phys. 1992, 96, 6880– 6890,  DOI: 10.1063/1.462582
      There is no corresponding record for this reference.
    47. 47
      Beniya, A.; Isomura, N.; Hirata, H.; Watanabe, Y. Low Temperature Adsorption and Site-Conversion Process of CO on the Ni(111) Surface. Surf. Sci. 2012, 606, 1830– 1836,  DOI: 10.1016/j.susc.2012.07.026
      47
      Low temperature adsorption and site-conversion process of CO on the Ni(111) surface
      Beniya, Atsushi; Isomura, Noritake; Hirata, Hirohito; Watanabe, Yoshihide
      Surface Science (2012), 606 (23-24), 1830-1836CODEN: SUSCAS; ISSN:0039-6028. (Elsevier B.V.)
      Low-temp. (25 K) adsorption states and the site conversion of adsorbed CO between the ontop and the hollow sites on Ni(111) were studied by temp. programmed desorption and IR reflection absorption spectroscopy. The activation energy and pre-exponential factor of desorption were estd. to be 1.2 eV and 2.6 × 1013 s-1, resp., in the limit of zero coverage. At low coverage, CO mols. preferentially adsorbed at the hollow sites <100 K. With increasing temp., the ontop sites were also occupied. Using a van't Hoff plot, the enthalpy and the entropy differences between the hollow and ontop CO were estd. to be 36 meV and 0.043 meV K-1, resp., and the vibrational entropy difference was estd. to be 0.085 meV K-1. The pos. entropy difference was the result of the low-energy frustrated translational mode of the ontop CO, which was estd. to be 4.6 meV. With the harmonic approxn., the upper limit of the activation energy of site hopping from ontop sites to hollow sites was estd. to be 61 meV. In addn., it was suggested that the activation energy of hollow-to-hollow site hopping via a bridge site was <37 meV.
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    48. 48
      Ge, Q.; King, D. Surface Diffusion Potential Energy Surfaces from First Principles: CO Chemisorbed on Pt{110}. J. Chem. Phys. 1999, 111, 9461– 9464,  DOI: 10.1063/1.480275
      48
      Surface diffusion potential energy surfaces from first principles: CO chemisorbed on Pt{110}
      Ge, Q.; King, D. A.
      Journal of Chemical Physics (1999), 111 (21), 9461-9464CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
      Lateral potential energy curves for the chemisorption of CO on Pt{110} (1×1) and (1×2) along different azimuthal directions were calcd. using d. functional theory slab calcns. In contrast to the simple models almost universally used, the results along 〈110〉 show that there is a barrier of ≈0.15 eV between bridge and atop sites. Both bridge and atop sites are local min. Diffusion along 〈100〉 on the (1×1) surface is strongly inhibited by a barrier ≥1.2 eV. Quasielastic He atom scattering data require reanal. in the light of these results. The free energy, detg. the most stable site at finite temps., includes a significant vibrational entropy term in the atop site.
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    49. 49
      Abild-Pedersen, F.; Andersson, M. CO Adsorption Energies on Metals with Correction for High Coordination Adsorption Sites–A Density Functional Study. Surf. Sci. 2007, 601, 1747– 1753,  DOI: 10.1016/j.susc.2007.01.052
      49
      CO adsorption energies on metals with correction for high coordination adsorption sites - A density functional study
      Abild-Pedersen, F.; Andersson, M. P.
      Surface Science (2007), 601 (7), 1747-1753CODEN: SUSCAS; ISSN:0039-6028. (Elsevier B.V.)
      We investigate the accuracy of carbon monoxide adsorption energies and site preferences for the metals Ag, Al, Au, Co, Cu, Fe, Ir, Mo, Ni, Pd, Pt, Re, Rh, Ru, W, and Zn using the RPBE functional with a recently suggested empirical adsorption energy correction for carbon monoxide based on the internal CO stretch vibrational frequency. We find that when including the correction, the adsorption site preference for six of the metals changes, and all adsorption site predictions become accurate. We also collect a large no. of exptl. studies for comparison with our calcd. adsorption energies. The mean abs. deviation including the correction is found to be less than 0.2 eV, showing that the RPBE functional gives a much better quant. agreement between expts. and calcns. than the PW91 functional.
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    50. 50
      Feibelman, P. J.; Hammer, B.; Nørskov, J. K.; Wagner, F.; Scheffler, M.; Stumpf, R.; Watwe, R.; Dumesic, J. The CO/Pt (111) Puzzle. J. Phys. Chem. B 2001, 105, 4018– 4025,  DOI: 10.1021/jp002302t
      50
      The CO/Pt(111) Puzzle
      Feibelman, Peter J.; Hammer, B.; Norskov, J. K.; Wagner, F.; Scheffler, M.; Stumpf, R.; Watwe, R.; Dumesic, J.
      Journal of Physical Chemistry B (2001), 105 (18), 4018-4025CODEN: JPCBFK; ISSN:1089-5647. (American Chemical Society)
      Notwithstanding half a dozen theor. publications, well-converged d.- functional calcns., whether based on a local-d. or generalized-gradient exchange-correlation potential, whether all-electron or employing pseudopotentials, underestimate CO's preference for low-coordination binding sites on Pt(111) and vicinals to it. For example, they imply that CO should prefer hollow- to atop-site adsorption on Pt(111), in apparent contradiction to a host of low-temp. exptl. studies.
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    51. 51
      Winterbottom, W. Equilibrium Shape of a Small Particle in Contact with a Foreign Substrate. Acta Metall. 1967, 15, 303– 310,  DOI: 10.1016/0001-6160(67)90206-4
      51
      Equilibrium shape of a small particle in contact with a foreign substance
      Winterbottom, Walter L.
      Acta Metallurgica (1967), 15 (2), 303-10CODEN: AMETAR; ISSN:0001-6160.
      A theory was developed for predicting the shapes of particles at interfaces. The analysis indicates that a generalized Gibbs-Wulff construction will predict the shape only when the particle-substrate (or grain boundary) interface is coplanar with the substrate surface (or grain boundary); otherwise, the construction is only an approxn. Application of the technique in the detn. of the γ-plot of Ag under ultrahigh-vacuum conditions was not possible because of the strong binding of the Ag film to the BeO substrates. Films of 99.999% Ag, 3000-5000 A. thick, were evapd. onto small, polished, high purity BeO disks at 25°. Deposition rates were 10 to 20 monolayers/sec.
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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF2sXnvVyntA%253D%253D&md5=7ac3abbce16b0b04e105b0a7e7dc5491
    52. 52
      Longwitz, S. R.; Schnadt, J.; Vestergaard, E. K.; Vang, R. T.; Lægsgaard, E.; Stensgaard, I.; Brune, H.; Besenbacher, F. High-Coverage Structures of Carbon Monoxide Adsorbed on Pt(111) Studied by High-Pressure Scanning Tunneling Microscopy. J. Phys. Chem. B 2004, 108, 14497– 14502,  DOI: 10.1021/jp0492218
      52
      High-coverage structures of carbon monoxide adsorbed on Pt(111) studied by high-pressure scanning tunneling microscopy
      Longwitz, Sarah R.; Schnadt, Joachim; Vestergaard, Ebbe Kruse; Vang, Ronnie T.; Lgsgaard, Erik; Stensgaard, Ivan; Brune, Harald; Besenbacher, Flemming
      Journal of Physical Chemistry B (2004), 108 (38), 14497-14502CODEN: JPCBFK; ISSN:1520-6106. (American Chemical Society)
      High-pressure scanning tunneling microscopy was used to study the room-temp. adsorption of CO on a Pt(111) single-crystal surface in equil. with the gas phase. The coverage was found to vary continuously, and over the entire range from 10-6-760 Torr pressure-dependent moire patterns were obsd., characteristic of a hexagonal or nearly hexagonal CO overlayer. Two different pressure ranges can be distinguished: below 10-2 Torr, the moire lattice vector is oriented along a 30° high-symmetry direction of the substrate, corresponding to a pressure-dependent rotation of the CO overlayer with respect to the (1 × 1) Pt surface lattice, while above 10-2 Torr, the CO layer angle is independent of the pressure. This behavior is analyzed in terms of the interplay of the repulsive CO-CO interaction potential and the substrate potential.
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    53. 53
      Ertl, G.; Neumann, M.; Streit, K. Chemisorption of CO on the Pt(111) Surface. Surf. Sci. 1977, 64, 393– 410,  DOI: 10.1016/0039-6028(77)90052-8
      53
      Chemisorption of carbon monoxide on the platinum(111) surface
      Ertl, G.; Neumann, M.; Streit, K. M.
      Surface Science (1977), 64 (2), 393-410CODEN: SUSCAS; ISSN:0039-6028.
      The system CO/Pt(111) was studied by LEED, thermal desorption, and work function measurements. At 170 K, a √3 × √3/R 30° structure at θ = 1/3 is continuously transformed with increasing coverage into a c4 × 2 structure at θ = 1/2 and finally into a hexagonal close-packed layer with satn. at ∼ θ = 0.68. Due to a decrease of the adsorption energy by ∼ 4 kcal/mol at θ = 0.5 (= 7.5 × 1014 mols./cm2) adsorption is completed at this coverage at room temp. The initial adsorption energy is ∼ 33 kcal/mol. A tendency for disordering below room temp. is shown by the LEED patterns and the Δ.vphi. data. The work function 1st decreases, exhibits a (temp.-dependent) min. at θ = 1/3, attains nearly the value of the clean surface at θ = 1/2, and again exhibits a 2nd (shallow) min. ∼ θ = 0.6. The obsd. effects may be explained by assuming the occupation of 2 adsorption sites at θ ≤ 0.5 with different dipole moments (presumably bridge (A) and 3-fold coordinated (B)) whose adsorption energy differs by only 0.5 kcal/mol. At low temps. at θ = 1/2 sites, A and at θ = 1/3 sites, B are preferentially occupied whereas their small energy difference favor disordering at increasing temp.
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    54. 54
      Kruse Vestergaard, E. K.; Thostrup, P.; An, T.; Lægsgaard, E.; Stensgaard, I.; Hammer, B.; Besenbacher, F. Comment on “High Pressure Adsorbate Structures Studied by Scanning Tunneling Microscopy: CO on Pt(111) in Equilibrium with the Gas Phase. Phys. Rev. Lett. 2002, 88, 259601,  DOI: 10.1103/PhysRevLett.88.259601
      There is no corresponding record for this reference.
    55. 55
      Parkinson, G. S.; Novotny, Z.; Argentero, G.; Schmid, M.; Pavelec, J.; Kosak, R.; Blaha, P.; Diebold, U. Carbon Monoxide-Induced Adatom Sintering in a Pd–Fe3O4 Model Catalyst. Nat. Mater. 2013, 12, 724– 728,  DOI: 10.1038/nmat3667
      55
      Carbon monoxide-induced adatom sintering in a Pd-Fe3O4 model catalyst
      Parkinson, Gareth S.; Novotny, Zbynek; Argentero, Giacomo; Schmid, Michael; Pavelec, Jiri; Kosak, Rukan; Blaha, Peter; Diebold, Ulrike
      Nature Materials (2013), 12 (8), 724-728CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
      The coarsening of catalytically active metal clusters is often accelerated by the presence of gases, but the role played by gas mols. is difficult to ascertain and varies from system to system. We use scanning tunnelling microscopy to follow the CO-induced coalescence of Pd adatoms supported on the Fe3O4(001) surface at room temp., and find Pd-carbonyl species to be responsible for mobility in this system. Once these reach a crit. d., clusters nucleate; subsequent coarsening occurs through cluster diffusion and coalescence. Whereas CO induces the mobility in the Pd/Fe3O4 system, surface hydroxyls have the opposite effect. Pd atoms transported to surface OH groups are no longer susceptible to carbonyl formation and remain isolated. Following the evolution from well-dispersed metal adatoms into clusters, atom-by-atom, allows identification of the key processes that underlie gas-induced mass transport.
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    56. 56
      Teschner, D.; Wootsch, A.; Pozdnyakova-Tellinger, O.; Kröhnert, J.; Vass, E.; Hävecker, M.; Zafeiratos, S.; Schnörch, P.; Jentoft, P.; Knop-Gericke, A. Partial Pressure Dependent in Situ Spectroscopic Study on the Preferential CO Oxidation in Hydrogen (PROX) over Pt/ceria Catalysts. J. Catal. 2007, 249, 318– 327,  DOI: 10.1016/j.jcat.2007.05.010
      56
      Partial pressure dependent in situ spectroscopic study on the preferential CO oxidation in hydrogen (PROX) over Pt/ceria catalysts
      Teschner, D.; Wootsch, A.; Pozdnyakova-Tellinger, O.; Kroehnert, J.; Vass, E. M.; Haevecker, M.; Zafeiratos, S.; Schnoerch, P.; Jentoft, P. C.; Knop-Gericke, A.; Schloegl, R.
      Journal of Catalysis (2007), 249 (2), 318-327CODEN: JCTLA5; ISSN:0021-9517. (Elsevier Ltd.)
      Platinum supported on ceria can oxidize CO in excess hydrogen selectively (PROX process). In situ DRIFTS and high-pressure (∼1 mbar) XPS expts. were performed to study the mechanism of the PROX reaction on Pt/ceria catalysts. The partial pressure of O2 and/or CO was varied and correlated with induced changes in activity and selectivity as well as with the surface state and species under reaction conditions. Pt-carbonyl species changed rather insignificantly, esp. relative to the wide variations of the product pattern with changing feed compn. Furthermore, the interconversion of formate and carbonate species was obsd. Therefore, the changes in the evolution of surface species detected by in situ DRIFTS cannot explain the variation obsd. in CO oxidn. activity. On the other hand, high-pressure XPS showed significant modification of the surface state with changing feed compn. Most significantly, oxygen vacancy formation seemed to correlate with enhanced CO oxidn. activity. At higher vacancy d., water desorption was hindered. Highly hydrated ceria with significant vacancy d. was found to be beneficial for the PROX process; here surface water blocked Hads oxidn. sites. Moreover, lower apparent activation energy of CO oxidn. was measured in the PROX reaction on catalysts with more vacancies. The results given here reinforce the view of catalysts being adaptive to a certain reaction rather than having active sites as prepd. Whereas IR-detectable surface species may only be indicators and/or consequences of this surface change, formation of the beneficial surface/near-surface state may be the rate-limiting factor in several catalytic processes.
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    57. 57
      Wadayama, T.; Todoroki, N.; Yamada, Y.; Sugawara, T.; Miyamoto, K.; Iijama, Y. Oxygen Reduction Reaction Activities of Ni/Pt(111) Model Catalysts Fabricated by Molecular Beam Epitaxy. Electrochem. Commun. 2010, 12, 1112– 1115,  DOI: 10.1016/j.elecom.2010.05.042
      57
      Oxygen reduction reaction activities of Ni/Pt(111) model catalysts fabricated by molecular beam epitaxy
      Wadayama, Toshimasa; Todoroki, Naoto; Yamada, Yoshinori; Sugawara, Tatsuya; Miyamoto, Kanji; Iijama, Yuki
      Electrochemistry Communications (2010), 12 (8), 1112-1115CODEN: ECCMF9; ISSN:1388-2481. (Elsevier B.V.)
      O redn. reaction (ORR) activities were evaluated for clean Pt(111) and Ni/Pt(111) model catalysts fabricated by MBE. Exposure of clean Pt(111) to 1.0 L CO at 303 K produced linear-bonded and bridge-bonded CO-Pt IR bands at 2093 and 1858 cm- 1. In contrast, 0.3-nm-thick Ni deposited on Pt(111) at 573 K (573 K-Ni0.3 nm/Pt(111)) produced broad IR bands for adsorbed CO at ∼2070 cm- 1; the sepn. of RHEED streaks is slightly wider for 573 K-Ni0.3 nm/Pt(111) than for the clean Pt(111). For 823 K-Ni0.3nm/Pt(111), the sepn. of the RHEED streaks is the same as that for the Pt(111), and a single sharp IR band due to adsorbed CO is located at 2082 cm- 1. Probably for the 823 K-Ni0.3 nm/Pt(111), a Pt-enriched outermost surface (Pt-skin) was formed through surface segregation of the substrate Pt atoms. ORR activities for the 573 K- and 823 K-Ni0.3 nm/Pt(111) as detd. from linear sweep voltammetry curves were five times and eight times higher than that for clean Pt(111), resp., demonstrating that Pt-skin generation is crucial for developing highly active electrode catalysts for fuel cells.
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    58. 58
      Heyden, B. E.; Bradshaw, A. M. The Adsorption of CO on Pt(111) Studied by Infrared-Reflection-Adsorption Spectroscopy. Surf. Sci. 1983, 125, 787– 802,  DOI: 10.1016/S0039-6028(83)80060-0
      There is no corresponding record for this reference.
    59. 59
      McCrea, K.; Parker, J. S.; Chen, P.; Somorjai, G. Surface Structure Sensitivity of High-Pressure CO Dissociation on Pt(557), Pt(100) and Pt(111) Using Sum Frequency Generation Surface Vibrational Spectroscopy. Surf. Sci. 2001, 494, 238– 250,  DOI: 10.1016/S0039-6028(01)01469-8
      59
      Surface structure sensitivity of high-pressure CO dissociation on Pt(5 5 7), Pt(1 0 0) and Pt(1 1 1) using sum frequency generation surface vibrational spectroscopy
      McCrea, Keith; Parker, Jessica S.; Chen, Peilin; Somorjai, Gabor
      Surface Science (2001), 494 (3), 238-250CODEN: SUSCAS; ISSN:0039-6028. (Elsevier Science B.V.)
      Using sum frequency generation (SFG) surface vibrational spectroscopy, the interaction of CO and Pt single crystals was investigated at high pressure and high temps. Under 40 Torr of CO, the mol. was found to dissoc. on Pt(1 1 1), Pt(5 5 7), and Pt(1 0 0) at 673, 548, and 500 K, resp. The CO top site frequency was obsd. to shift to lower frequencies as a function of temp. At a particular temp., dependent on the surface structure, the SFG spectra evolved with time, indicating the surface was being modified. The obsd. frequency shift before CO dissocn. is attributed to anharmonic coupling to the frustrated translational mode. At the temp. at which dissocn. occurs, the frequency shift is attributed to surface roughening. The surface roughening is believed to result from the formation of platinum carbonyl species, which would be a driving force to ext. platinum atoms from the surface lattice. For both the (1 1 1) and (1 0 0) surfaces of Pt, the crystal must be heated to a temp. at which platinum carbonyls are formed to produce step and kink sites, which are needed for dissocn. The Pt(1 1 1) surface exhibits a much higher CO dissocn. temp. as compared to Pt(1 0 0) because it is the most stable surface for Pt. Pt(5 5 7) is essentially a (1 1 1) surface with steps already present in the structure, and so the crystal does not need to be heated to a temp. to produce step and kink sites necessary for CO dissocn. through the prodn. of Pt carbonyls. CO can dissoc. on the existing steps of Pt(5 5 7).
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    60. 60
      Gajdoš, M.; Eichler, A.; Hafner, J. CO Adsorption on Close-Packed Transition and Noble Metal Surfaces: Trends from ab initio Calculations. J. Phys.: Condens. Matter 2004, 16, 1141,  DOI: 10.1088/0953-8984/16/8/001
      60
      CO adsorption on close-packed transition and noble metal surfaces: trends from ab initio calculations
      Gajdos, Marek; Eichler, Andreas; Hafner, Juergen
      Journal of Physics: Condensed Matter (2004), 16 (8), 1141-1164CODEN: JCOMEL; ISSN:0953-8984. (Institute of Physics Publishing)
      A review. The trends in CO adsorption on close-packed metal surfaces Co, Ni, Cu from the 3d row, Ru, Rh, Pd, Ag from the 4d row and Ir, Pt, Au from the 5d row were studied using d. functional theory. In particular, the trends in adsorption energy, geometry, vibrational properties, and other parameters derived from the electronic structure of the substrate were concerned. The influence of specific changes in our set-up, such as choice of the exchange correlation functional, the choice of pseudopotential, size of the basis set and substrate relaxation, was carefully evaluated. While the geometrical and vibrational properties of the adsorbate-substrate complex are calcd. with high accuracy, the adsorption energies calcd. with the gradient-cor. Perdew-Wang exchange-correlation energies are overestimated. Tn addn., the calcns. tend to favor adsorption sites with higher coordination, resulting in the prediction of the wrong adsorption sites for the Rh, Pt, and Cu surfaces (hollow instead of top). The revised Perdew-Burke-Erzernhof functional (RPBE) leads to lower (i.e. more realistic) adsorption energies for transition metals, but to the wrong results for noble metals-for Ag and Au, endothermic adsorption is predicted. The site preference remains the same. The trends in relation to the electronic structure of the substrate across the periodic table are discussed, summarizing the state-of-the-art of CO adsorption on close-packed metal surfaces.
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    61. 61
      Bazin, P.; Saur, O.; Lavalley, J.; Daturi, M.; Blanchard, G. FT-IR Study of CO Adsorption on Pt/CeO2: Characterisation and Structural Rearrangement of Small Pt Particles. Phys. Chem. Chem. Phys. 2005, 7, 187– 194,  DOI: 10.1039/b414159h
      61
      FT-IR study of CO adsorption on Pt/CeO2: characterization and structural rearrangement of small Pt particles
      Bazin, P.; Saur, O.; Lavalley, J. C.; Daturi, M.; Blanchard, G.
      Physical Chemistry Chemical Physics (2005), 7 (1), 187-194CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
      CO adsorption has been followed by IR spectroscopy on a Pt/CeO2 sample (Pt loading = 0.5%) treated under oxygen and vacuum or reduced by H2 and then evacuated at various temps. The sample contains highly dispersed Pt. Attention is paid to the presence of an unusual ν(CO) band at 1937 cm-1 on the reduced sample. Such a band is in particular not obsd. when the support is fully covered by CO (CO adsorption at liq. nitrogen temp.) or by methanol, allowing one to assign it to CO bridged species bound to both Pt very lowly coordinated and to the support, e.g. to sites at the periphery of very small Pt particles. Expts. performed after sample redn. at 423 K followed by increasing evacuation temp. between 423 and 673 K showed that the increase of the latter provokes a sintering of the Pt particles, due to ceria surface O2- mobility.
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    62. 62
      Pozdnyakova-Tellinger, O.; Teschner, D.; Kröhnert, J.; Jentoft, F. C.; Knop-Gericke, A.; Schlögl, R.; Wootsch, A. Surface Water-Assisted Preferential CO Oxidation on Pt/CeO2 Catalyst. J. Phys. Chem. C 2007, 111, 5426– 5431,  DOI: 10.1021/jp0669862
      62
      Surface Water-Assisted Preferential CO Oxidation on Pt/CeO2 Catalyst
      Pozdnyakova-Tellinger, Olga; Teschner, Detre; Kroehnert, Jutta; Jentoft, Friederike C.; Knop-Gericke, Axel; Schloegl, Robert; Wootsch, Attila
      Journal of Physical Chemistry C (2007), 111 (14), 5426-5431CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      The prodn. of clean hydrogen is a key requirement for a future hydrogen economy, in general, and, specifically, for the application of proton exchange membrane fuel cells (PEMFC). Here, we focus on one of the essential purifn. methods, the so-called preferential oxidn., "PROX" reaction, of traces of CO in a large hydrogen excess. Small platinum particles on a reducible support like ceria are effective to remove CO from hydrogen feed. The paper specifically addresses the mechanism of the PROX reaction on a Pt/CeO2 catalyst using in situ experimentation with time-resolved and temp.-programmed diffuse reflectance IR spectroscopy. Surface species (carbonates, formates, carbonyls, hydroxyls, and adsorbed water) present under reaction conditions are identified, and correlations of their abundance with catalytic performance allow the discrimination between mechanistically relevant species (intermediates) and spectator species. The following scenario is proposed: hydrogen initially adsorbed on platinum spills over to the support, leading to ordered vacancy formation in the ceria bulk as well as hydroxylation and hydration of the surface. CO is mainly adsorbed in on-top orientation on metallic platinum. The linear relationship between the amt. of adsorbed water (H2Oads) and the CO2 prodn. indicates that the hydrated ceria supplies an oxidizing agent at the metal/support interface reacting with the nearby surface carbonyls on the Pt particles yielding CO2. Moreover, adsorbed water also blocks hydrogen oxidn. because of desorption hindrance. From the correlations in the presented results, an intelligent PROX catalyst can be formulated, providing a guideline for future developments.
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    63. 63
      Ding, K.; Gulec, A.; Johnson, A. M.; Schweitzer, N. M.; Stucky, G. D.; Marks, L. D.; Stair, P. C. Identification of Active Sites in CO Oxidation and Water-Gas Shift over Supported Pt Catalysts. Science 2015, 350, 189– 192,  DOI: 10.1126/science.aac6368
      63
      Identification of active sites in CO oxidation and water-gas shift over supported Pt catalysts
      Ding, Kunlun; Gulec, Ahmet; Johnson, Alexis M.; Schweitzer, Neil M.; Stucky, Galen D.; Marks, Laurence D.; Stair, Peter C.
      Science (Washington, DC, United States) (2015), 350 (6257), 189-192CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
      Identification and characterization of catalytic active sites are the prerequisites for an at.-level understanding of the catalytic mechanism and rational design of high-performance heterogeneous catalysts. Indirect evidence in recent reports suggests that platinum (Pt) single atoms are exceptionally active catalytic sites. We demonstrate that IR spectroscopy can be a fast and convenient characterization method with which to directly distinguish and quantify Pt single atoms from nanoparticles. In addn., we directly observe that only Pt nanoparticles show activity for carbon monoxide (CO) oxidn. and water-gas shift at low temps., whereas Pt single atoms behave as spectators. The lack of catalytic activity of Pt single atoms can be partly attributed to the strong binding of CO mols.
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    64. 64
      Moses-DeBusk, M.; Yoon, M.; Allard, L. F.; Mullins, D. R.; Wu, Z.; Yang, X.; Veith, G.; Stocks, G. M.; Narula, C. K. CO Oxidation on Supported Single Pt Atoms: Experimental and ab initio Density Functional Studies of CO Interaction with Pt atom on θ-Al2O3(010) Surface. J. Am. Chem. Soc. 2013, 135, 12634– 12645,  DOI: 10.1021/ja401847c
      64
      CO Oxidation on Supported Single Pt Atoms: Experimental and ab Initio Density Functional Studies of CO Interaction with Pt Atom on θ-Al2O3(010) Surface
      Moses-DeBusk, Melanie; Yoon, Mina; Allard, Lawrence F.; Mullins, David R.; Wu, Zili; Yang, Xiaofan; Veith, Gabriel; Stocks, G. Malcolm; Narula, Chaitanya K.
      Journal of the American Chemical Society (2013), 135 (34), 12634-12645CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Although there are only a few known examples of supported single-atom catalysts, they are unique because they bridge the gap between homogeneous and heterogeneous catalysis. Here, we report the CO oxidn. activity of monodisperse single Pt atoms supported on an inert substrate, θ-alumina (Al2O3), in the presence of stoichiometric oxygen. Since CO oxidn. on single Pt atoms cannot occur via a conventional Langmuir-Hinshelwood scheme (L-H scheme) which requires at least one Pt-Pt bond, we carried out a first-principles d. functional theor. study of a proposed pathway which is a variation on the conventional L-H scheme and inspired by the organometallic chem. of platinum. We find that a single supported Pt atom prefers to bond to O2 over CO. CO then bonds with the oxygenated Pt atom and forms a carbonate which dissocs. to liberate CO2, leaving an oxygen atom on Pt. Subsequent reaction with another CO mol. regenerates the single-atom catalyst. The energetics of the proposed mechanism suggests that the single Pt atoms will get covered with CO3 unless the temp. is raised to eliminate CO2. We find evidence for CO3 coverage at room temp. supporting the proposed mechanism in an in situ diffuse reflectance IR study of CO adsorption on the catalyst's supported single atoms. Thus, our results clearly show that supported Pt single atoms are catalytically active and that this catalytic activity can occur without involving the substrate. Characterization by electron microscopy and X-ray absorption studies of the monodisperse Pt/θ-Al2O3 are also presented.
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    65. 65
      Wu, T.; Pan, X.; Zhang, Y.; Miao, Z.; Zhang, B.; Li, J.; Yang, X. Investigation of the Redispersion of Pt Nanoparticles on Polyhedral Ceria Nanoparticles. J. Phys. Chem. Lett. 2014, 5, 2479– 2483,  DOI: 10.1021/jz500839u
      65
      Investigation of the Redispersion of Pt Nanoparticles on Polyhedral Ceria Nanoparticles
      Wu, Tianxiao; Pan, Xiqiang; Zhang, Yibo; Miao, Zhenzhen; Zhang, Bin; Li, Jingwei; Yang, Xiangguang
      Journal of Physical Chemistry Letters (2014), 5 (14), 2479-2483CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      Redispersion of Pt nanoparticles on ceria with defined surface planes including cubes ({100}) and octahedra ({111}) has been studied. The Pt redispersion takes place only on ceria cubes in an alternating oxidn. and redn. atm. A quicker alternation rate is beneficial for such redispersion. The authors propose that the redispersion takes place at the moment of alternation of oxidn. and redn.
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    66. 66
      Su, Y. Q.; Filot, I. A. W.; Liu, J. X.; Hensen, E. J. M. Stable Pd-Doped Ceria Structures for CH4 Activation and CO Oxidation. ACS Catal. 2018, 8, 75– 80,  DOI: 10.1021/acscatal.7b03295
      66
      Stable Pd-Doped Ceria Structures for CH4 Activation and CO Oxidation
      Su, Ya-Qiong; Filot, Ivo A. W.; Liu, Jin-Xun; Hensen, Emiel J. M.
      ACS Catalysis (2018), 8 (1), 75-80CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
      Doping CeO2 with Pd atoms has been assocd. with catalytic CO oxidn., but current surface models do not allow CO adsorption. Here, we report a new structure of Pd-doped CeO2(111), in which Pd adopts a square planar configuration instead of the previously assumed octahedral configuration. Oxygen removal from this doped structure is favorable. The resulting defective Pd-doped CeO2 surface is active for CO oxidn. and is also able to cleave the first C-H bond in methane. We show how the moderate CO adsorption energy and dynamic features of the Pd atom upon CO adsorption and CO oxidn. contribute to a low-barrier catalytic cycle for CO oxidn. These structures, which are also obsd. for Ni and Pt, can lead to a more open coordination environment around the doped-transition-metal center. These thermally stable structures are relevant to the development of single-atom catalysts.
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    67. 67
      Su, Y. Q.; Liu, J. X.; Filot, I. A. W.; Zhang, L.; Hensen, E. J. M. Highly Active and Stable CH4 Oxidation by Substitution of Ce4+ by two Pd2+ Ions in CeO2(111). ACS Catal. 2018, 8, 6552– 6559,  DOI: 10.1021/acscatal.8b01477
      67
      Highly Active and Stable CH4 Oxidation by Substitution of Ce4+ by Two Pd2+ Ions in CeO2(111)
      Su, Ya-Qiong; Liu, Jin-Xun; Filot, Ivo A. W.; Zhang, Long; Hensen, Emiel J. M.
      ACS Catalysis (2018), 8 (7), 6552-6559CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
      Methane (CH4) combustion is an increasingly important reaction for environmental protection, for which Pd/CeO2 has emerged as the preferred catalyst. There is a lack of understanding of the nature of the active site in these catalysts. Here, we use d. functional theory to understand the role of doping of Pd in the ceria surface for generating sites highly active toward the C-H bonds in CH4. Specifically, we demonstrate that two Pd2+ ions can substitute one Ce4+ ion, resulting in a very stable structure contg. a highly coordinated unsatd. Pd cation that can strongly adsorb CH4 and dissoc. the first C-H bond with a low energy barrier. An important aspect of the high activity of the stabilized isolated Pd cation is its ability to form a strong σ-complex with CH4, which leads to effective activation of CH4. We show that also other transition metals like Pt, Rh, and Ni can give rise to similar structures with high activity toward C-H bond dissocn. These insights provide us with a novel structural view of solid solns. of transition metals such as Pt, Pd, Ni, and Rh in CeO2, known to exhibit high activity in CH4 combustion.
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    68. 68
      Kopelent, R.; van Bokhoven, J. A.; Szlachetko, J.; Edebeli, J.; Paun, C.; Nachtegaal, M.; Safonova, O. V. Catalytically Active and Spectator Ce3+ in Ceria-Supported Metal Catalysts. Angew. Chem. 2015, 127, 8852– 8855,  DOI: 10.1002/ange.201503022
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  • Supporting Information

    Supporting Information

    The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acscatal.9b00252.

    • Derivation of the dispersion formula; critical size diagrams of supported Pt NPs and frequency analyses of CO bound to Pt facets; kinetic data of Pt atom dislodging from Pt4 and Pt8 supported on CeO2(111); DFT-determined catalytic cycles of CO oxidation and GT-kMC data (PDF)


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