PdAu Surface Research Articles

A combination of DFT and kMC to study on the formation mechanism of ethyl acetate during the gas-phase synthesis of vinyl acetate from ethylene on PdAu(100) surface

Vinyl acetate (VAc) is an important chemical raw material for the production of polyvinyl alcohol and polyvinyl acetate, among others. The preparation of vinyl acetate over PdAu catalysts using ethylene, oxygen and acetic acid as raw materials is one of the mainstream processes for the production of vinyl acetate in the world. The by-product ethyl acetate in this process is more difficult to be completely removed, and it is an impurity component in vinyl acetate products that needs to be strictly controlled in content. However, studies on the mechanism of ethyl acetate generation have not been reported, which limits the improvement of the purity of vinyl acetate products and the optimization of the ethyl acetate separation process. In this paper, the mechanism of ethyl acetate generation during ethylene vinyl acetate reaction on PdAu catalysts was systematically investigated using a combination of density functional theory (DFT) and kinetic Monte Carlo (kMC) simulations.The results show that the species tend to adsorb to the Pd-Au bridge sites, diagonal Pd-Pd vacancies, and diagonal Pd-Au vacancies of PdAu(100), and the Pd on the catalyst surface interacts more strongly with the adsorbed species. The dominant pathway for the generation of ethyl acetate on PdAu(100) is CH2CH2* + O*→ CH2CH* + H* → CH3CH* + CH3COO* → CH3COOCHCH3* + H* → CH3COOCH2CH3*, where the hydrogenation of CH2CH* to CH3CH* is the rate-control step in the dominant pathway for the generation of ethyl acetate. This step has an energy barrier of 1.09 eV and a reaction heat of 0.90 eV. The study of the generation mechanism of the by-product ethyl acetate in this paper is hoped to provide more targeted guidance and suggestions for the modification of Pd-Au catalysts, so as to reduce the generation of ethyl acetate as a by-product, to reduce the energy consumption required for the separation, and to enhance the purity of vinyl acetate products.

Mechanistic study of the production of ethylene glycol diacetate as a byproduct of the ethylene vapor phase process for vinyl acetate on PdAu(100) surface

With the rapid development of the photovoltaic industry, the demand for new materials such as EVA resin is increasing, and the study of its synthetic monomer vinyl acetate is of great significance. The ethylene vapor phase process is the current mainstream method for producing ethylene acetate. This method mainly uses a PdAu bimetallic catalyst to catalyze the production of ethylene acetate and water from ethylene, acetic acid and oxygen. The reaction process produces ethylene glycol diacetate, a high boiling point byproduct, which not only increases the energy consumption for separating the byproduct and reduces the selectivity of the target product but also may lead to catalyst deactivation. Therefore, reducing its production is of great importance in industrial production. The production mechanism of ethylene glycol diacetate is not clear due to the large variety of surface species and the complexity of the reaction in the ethylene vapor phase method, which makes it challenging to investigate the production mechanism of ethylene glycol diacetate directly by experimental means without interference. Molecular simulation techniques, especially Density Functional Theory (DFT) simulations and kinetic Monte Carlo (kMC) simulations, allow for a targeted study of the catalyst surface reaction mechanism to obtain the mechanism of ethylene glycol diacetate production.In this paper, the elementary reaction in the possible formation path of ethylene glycol diacetate on PdAu(100) surface has been studied by the DFT simulations, and the energy barrier and reaction heat of each elementary reaction have been obtained. Moreover, based on the DFT simulation data, the generation process of ethylene glycol diacetate on PdAu(100) surface is investigated by the kMC simulation, including the processes of reactant adsorption, intermediate species diffusion, surface reaction, and product desorption. The calculation results show that the species are mainly adsorbed on the Pd-Au bridge site or Pd top site; ethylene can firstly generate CH3COOCH2CH2, CH3COOCHCH2 or CH3COOCHCH species and then be combined with CH3COO species to produce ethylene glycol diacetate, where the energy barrier of the reaction of CH3COOCH2CH2 species with CH3COO species is lower than other two species with CH3COO species. The advantage generation path for the ethylene glycol diacetate on PdAu(100) surface is CH2CH2→CH3COOCH2CH2→CH3COOCH2CH2OCOCH3, and the rate-determining step is the reaction of ethylene with CH3COO species to form CH3COOCH2CH2 species.

Theoretical insights into the dissociation and oxidation of ethylene during vinyl acetate synthesis

Gas phase synthesis of vinyl acetate from ethylene over Pd-Au catalyst is one of the mainstream processes. During the synthesis of vinyl acetate, the surface C generated by the dissociation of ethylene can be doped into the lattice of Au to form interstitial C. The synergistic effect of interstitial C and Au can promote the production of vinyl acetate. However, the formation mechanism of surface C is not clear. In addition, CO2 is formed during the dissociation and oxidation of ethylene. In order to reduce carbon emissions, it is also necessary to clarify the formation mechanism of CO2. In this study, the reaction mechanism for the dissociation and oxidation of ethylene on the PdAu(100) surface was investigated by density functional theory and kinetic Monte Carlo, and the formation pathways of surface C and CO2 were clarified.The results show that the generation pathway of surface C is CH2CH2→ CH2CH→ CHCH→ CHC→ CC→ CCO→ C+CO. The rate control step is CCO→C + CO with energy barrier of 1.39 eV and reaction heat of 0.52 eV. The generation pathway of CO2 is C → COH → CO → CO2. The rate control step is C+OH→COH with energy barrier of 0.71 eV and reaction heat of -1.12 eV. Clarification of the reaction mechanism for dissociation and oxidation of ethylene on the PdAu(100) surface and the formation pathways of surface C and CO2 can more specifically reduce the consumption of ethylene for by-products, better construct the synergism of surface C and Au, and reduce the emission of CO2 in the process of catalyst improvement and optimization.

Theoretical insight into the generation mechanism of vinyl acrylate in the production of vinyl acetate on PdAu(100)

Possible reaction network for the formation of vinyl acrylate on PdAu(100) surface.

Theoretical insight into the effect of impurity on the acetoxylation of ethylene to form vinyl acetate: A DFT study of acetylene coversion on PdAu(1 0 0) surface

Vinyl acetate (VA) is an important organic chemical material, which is mainly obtained from ethylene acetoxylation. The raw material, ethylene, usually contains a small amount of acetylene. To understand the effect of acetylene on vinyl acetate system, we used density functional theory (DFT) to explore the pathways and the main products of acetylene conversion on PdAu(100) surface. DFT calculation results suggest that acetylene is quite active on PdAu(100) surface and the Pd-Au catalyst can catalyze the oxidation, hydrogenation and polymerization reaction of acetylene. In all reactions, oxidation reaction is the most likely to occur due to low energy barrier. CO2 and aldehydes as oxidation products will exist simultaneously in the reaction system. Hydrogenation and polymerization of acetylene have a mute effect on vinyl acetate system. We can draw a preliminary conclusion that trace acetylene has little effect on vinyl acetate system.

A density functional theory study on the effect of acetylene on vinyl acetate synthesis from acetoxylation of ethylene over Pd-Au catalysts

In this work, the reaction network of acetylene on Pd-Au catalyst was constructed firstly, and the single adsorption configurations and adsorption energies and electronic properties of key species in the reaction network were calculated with Density Functional Theory (DFT). It was found that most of the species tend to be adsorbed on the sites around Pd atoms and acetylene does not occupy the active site of ethylene. Then the energy barrier and reaction energy of the related reaction of acetylene on the Pd-Au surface and the geometric configuration of the transition state were calculated through DFT. Acetylene is highly reactive and oxidation, hydrogenation and polymerization were easy to occur. Among all the reactions, the oxidation reaction had the most competitive advantage. CO2 was the most in the final product, followed by the intermediate product C2H3. CO2 and C2H3 have no adverse effect on the reaction system, so the trace of acetylene in the raw material ethylene had a very weak effect on the vinyl acetate reaction system.

On Surface Oxidation Issues Arising during CO Oxidation on a PdAu(110) Surface. An In Situ Study by Complementary Environmental Methods (STM, SXRD, XPS)

On Surface Oxidation Issues Arising during CO Oxidation on a PdAu(110) Surface. An <i>In Situ</i> Study by Complementary Environmental Methods (STM, SXRD, XPS)

Development and Characterization of a One-Pot Synthesized Fe–Au–Pd Surface Alloy Catalyst for Highly Selective Conversion of Castor Oil to Octadecane via Hydrodeoxygenation

Development and Characterization of a One-Pot Synthesized Fe–Au–Pd Surface Alloy Catalyst for Highly Selective Conversion of Castor Oil to Octadecane via Hydrodeoxygenation

Surface segregation of PdM (M=Cu, Ag, Au) alloys and its implication to acetylene hydrogenation, DFT-based Monte Carlo simulations

The surface composition and atomic arrangement of heterogeneous catalysts determine the surface chemistry and are necessary information for understanding surface catalytic reactions. Compared with monometallic catalysts, alloy catalysts are more complicated because of possible surface segregation or adsorption-induced segregation which may change under different reaction atmosphere. Construction of reasonable slab models to study reactions on alloy surfaces is of importance. Here we proposed a density functional theory based Monte Carlo method (DFT-MC) and used it to investigate the surface composition and atomic arrangement of the (111) surfaces of 1:1 PdAg, PdAu and PdCu alloys in vacuum and under the acetylene partial hydrogenation conditions modeled by co-adsorption of H and acetylene and of H and ethylene. Our DFT-MC simulations indicate that Au and Ag segregate on the PdAu(111) and PdAg(111) surfaces while Pd is enriched on the PdCu(111) surface under vacuum conditions. The surface Pd contents of PdAg and PdAu tend to increase under partial hydrogenation conditions. Analyses reveal that the co-adsorption energies on the ideal (bulk-cut) surfaces correlate linearly with the values on the segregated surfaces and there is also a linear relationship for the d-band centers between the ideal and segregated surfaces. The present study provides a way to construct more realistic models for studying reactions on alloy surfaces.

Electrochemical Reaction and Dissociation of Glycerol on PdAu Surface Catalyst

Direct Glycerol Fuel Cell is one of the alternative energy that can produce electricity without burning. The production of electricity without combustion can reduce the use of fossil fuel as well as reduce environmental pollution. A new catalyst of PdAu has been synthesized in this study to increase the activity of the glycerol oxidation reaction. Morphologies analysis was performed on CNF-supported synthesized PdAu. FESEM and TEM image show the PdAu supported on the CNF surface. Both PdAu and CNF has a diameter size of 4-6 nm and 80-130 nm, respectively. In CV analysis, PdAu/CNF has produced an oxidation peak and current density at -0.9 V vs. SCE and 70 mA/cm2, respectively. Each mechanism of glycerol dissociation step during glycerol oxidation, different atomic active sites are required in PdAu. For example, for glycerol adsorption, Au atom as an active site while for *C3H7O3 requires Pd atom and Au atom as the active site. The Au catalyst model shows better adsorption as Au/CNF has a slightly more negative oxidation peak than PdAu. Nevertheless, the Au catalyst showed less durability compared to PdAu.

Catalytic Reactions on Pd-Au Bimetallic Model Catalysts.

ConspectusThe enhanced catalytic activity of Pd-Au catalysts originates from ensemble effects related to the local composition of Pd and Au. The study of Pd-Au planar model catalysts in an ultrahigh vacuum (UHV) environment allows the observation of molecular level catalytic reactions between the Pd-Au surface and target molecules. Recently, there has been progress in understanding the behavior of simple molecules (H2, O2, CO, etc.) employing UHV surface science techniques, the results of which can be applied not only to heterogeneous catalysis but also to electro- and photochemical catalysis.Employing UHV methods in the investigation of Pd-Au model catalysts has shown that single Pd atoms can dissociatively adsorb H2 molecules. The recombinative desorption temperature of H2 varies with Pd ensemble size, which allows the use of H2 as a probe molecule for quantifying surface composition. In particular, H2 desorption from Pd-Au interface sites (or small Pd ensembles) is observed from 150-300 K, which is between the H2 desorption temperature from pure Au (∼110 K) and Pd (∼350 K) surfaces. When the Pd ensembles are large enough to form Pd(111)-like islands, H2 desorption occurs from 300-400 K, as with pure Pd surfaces. The different H2 desorption behavior, which depends on Pd ensemble size, has also been applied to the analysis of dehydrogenation mechanisms for potential liquid storage mediums for H2, namely formic acid and ethanol. In both cases, the Pd-Au interface is the main reaction site for generating H2 from formic acid and ethanol with less overall decomposition of the two molecules (compared to pure Pd).The chemistry behind O2 activation has also been informed through the control of Pd ensembles on a gold model catalyst for acetaldehyde and ethanol oxidation reactions under UHV conditions. O2 molecules molecularly adsorbed on continuous Pd clusters can be dissociated into O adatoms above 180 K. This O2 activation process is improved by coadsorbed H2O molecules. It is also possible to directly (through a precursor mechanism) introduce O adatoms on the Pd-Au surface by exposure to O2 at 300 K. The quantity of dissociatively adsorbed O adatoms is proportional to the Pd coverage. However, the O adatoms are more reactive on a less Pd covered surface, especially at the Pd-Au interface sites, which can initiate CO oxidation at temperatures as low as 140 K. Acetaldehyde molecules can be selectively oxidized to acetic acid on the Pd-Au surface with O adatoms, in which the selectivity toward acetic acid originates from preventing the decarboxylation of acetate species. Moreover, the O adatoms on the Pd-Au surface accelerate ethanol dehydrogenation, which causes the increase in acetaldehyde production. Hydrogen is continuously abstracted from the formed acetaldehyde and remaining ethanol molecules, and they ultimately combine as ethyl acetate on the Pd-Au surface.Using Pd-Au model catalysts under UHV conditions allows the discovery of molecular level mechanistic details regarding the catalytic behavior of H and O adatoms with other molecules. We also expect that these findings will be applicable regarding other chemistry on Pd-Au catalysts.

The mechanism of methanol dehydrogenation on the PdAu(1 0 0) surface: A DFT study

Density functional theory (DFT) was employed to investigate the mechanism of CH3OH dehydrogenation on the PdAu(1 0 0) surface. The adsorption of intermediates involved in the methanol dehydrogenation process was identified and all the elementary reactions were calculated. The route 3 “CH3OH → CH2OH → CHOH → CHO → CO” is determined as the most preferable pathway, of which the rate-limiting step is the dehydrogenation of CH3OH to CH2OH. PdAu has an enhanced catalytic performance towards MOR comparing to the monometallic Pd and Au systems. The strengthened adsorption of CH3OH and the decreased energy barrier of the rate-limiting step account for the enhanced activity, while the weaker CO adsorption contributes to the better anti-poisoning ability. On the PdAu(1 0 0) surface, Pd atoms play as the active sites while Au strengthens the activity and poisoning tolerance of the neighboring Pd. The synergistic effect of PdAu is explained by the d-band theory. The upshifted d-band center suggests that the Pd atoms on the PdAu(1 0 0) surface are more active than those on the Pd(1 0 0) surface. Our theoretical study reveals the mechanism of CH3OH dehydrogenation on the PdAu(1 0 0) surface, which is in favor of the further optimization of the promising non-platinum PdAu catalysts for DMFCs.

Highly Efficient AuPd Catalyst for Synthesizing Polybenzoxazole with Controlled Polymerization

Summary Using nanoparticles (NPs) to catalyze chemical reactions for the formation of functional polymers with controlled polymerization is an important field of chemical research. In this article, we report an AuPd NP system as an active and stable catalyst to catalyze one-pot reaction of formic acid, 1,5-diisopropoxy-2,4-dinitrobenzene, and terephthaldehyde, leading to the controlled polymerization and the formation of polybenzoxazole (PBO) (Mw = 3.6 kDa). The one-pot reaction is AuPd NP size and composition dependent, and 8-nm Au39Pd61 NPs are the best catalyst for the polymerization. The highly pure PBO shows excellent thermal stability up to 600°C and improved chemical and mechanical stability under challenging environmental conditions compared with commercial PBO (Zylon, Mw = 40 kDa). The reported NP-catalyzed one-pot reaction to polymerization is not limited to the formation of PBO but can be extended as a general approach to rigid polymers that are important for ballistic fiber, anti-flame, and smart-textile applications.

Pd-Shaped Nanoparticles Modified by Gold ad-Atoms: Effects on Surface Structure and Activity Toward Glucose Electrooxidation.

Palladium nanoparticles (Pd-NPs) with controlled distributions of sizes and shapes (nanospheres–Pd-NS-, nanocubes -Pd-NC-, and nanooctahedrons -Pd-NO-) are synthesized by wet chemistry methods and characterized by TEM/HRTEM. The surfaces of Pd-NPs are modified by spontaneous adsorption of gold and characterized by cyclic voltammetry in acidic medium. It is shown that the modification of Pd-NPs by dipping in HAuCl4 solutions of different concentrations allows controlling the surface coverage by gold. It is also shown that the modification of Pd-NPs surfaces involves first the formation of PdAu surface alloys. For higher coverages, both PdAu surface alloys and pure Au structures are formed. The activity toward the glucose electrooxidation reaction is determined by linear scan voltammetry (LSV). Higher activity is observed on pure Pd-NC presenting extended (100) surfaces than on Pd-NO with mainly (111) surface orientation and on Pd-NS without preferential surface orientation, both these latter Pd-NPs displaying almost the same activity. The modification of the surface by spontaneous adsorption of gold greatly improves the activity of all Pd-NPs. However, Au-modified Pd-NC materials remain the most active catalysts. PdAu surface alloys seem to be involved in the improvement of the catalytic activity at low potentials, although the role of pure gold structures on Pd-NPs toward the enhancement of the catalytic activity cannot be excluded for high gold coverage. The study allows a better understanding of the material structure/electrocatalytic behavior relationship.

Oxidative Cross-Esterification and Related Pathways of Co-Adsorbed Oxygen and Ethanol on Pd–Au

Ethanol is one of the most important industrial chemicals considering its wide range of uses. From ultrahigh vacuum (UHV) experiments, we were able to effectively produce acetaldehyde and ethyl acetate on a Pd–Au model catalyst. The presence of oxygen at the Pd–Au interface sites was found to be highly reactive for ethanol dehydrogenation, significantly increasing acetaldehyde production and promoting cross-esterification to produce ethyl acetate. Density functional theory calculations show that compared to the bare PdAu(111) surface, the presence of preadsorbed oxygen and the subsequently formed hydroxyl group leads to highly active and selective initial ethanol dehydrogenation at the O–H and α–C-H position, which was corroborated by isotope-labeling experiments. Specifically, using temperature-programmed desorption with the isotope CD3CH2OH, we identified C–C bond breakage through methane production. Furthermore, the simultaneous desorption of D2 with ethyl acetate from the oxidation of CD3CD2OD suggest...

Selective Oxidation of Acetaldehyde to Acetic Acid on Pd–Au Bimetallic Model Catalysts

Acetic acid is a widely employed reactant in the chemical industry, and it is also used as a food ingredient. Here, we report a catalytic reaction pathway for the gas-phase selective oxidation of acetaldehyde to acetic acid on a Pd–Au(111) heterogeneous model catalyst. On an oxygen precovered Pd–Au surface, acetaldehyde is selectively oxidized to acetic acid from 250 to 340 K. Using FT-IR, the formation of acetate species is detected from 160 to 260 K on this surface, which is a widely known adsorbate derived from acetic acid on metal surfaces. With higher Pd coverages, the acetaldehyde is less selectively oxidized to acetic acid, and near 375 K, CO2, H2O, CH4, and H2 are evolved, evidence for the decarboxylation of acetate. In our density functional theory calculations, we confirm that the relative energy difference between the acetate state and the decarboxylated state decreases as Pd ensemble size increases.

Voltage effects on the stability of Pd ensembles in Pd-Au/Au(111) surface alloys.

The catalytic performance of multimetallic electrodes is often attributed to a beneficial combination of ligand, strain, and ensemble effects. Understanding the influence of the electrochemical environment on the stability of the alloy surface structure is thus a crucial component to the design of highly active and durable electrocatalysts. In this work, we study the effects of an applied voltage to electrocatalytic Pd-Au/Au(111) surface alloys in contact with a model continuum electrolyte. Using planewave density functional theory, two-dimensional cluster expansions are parameterized and used to simulate dilute Pd-Au surface alloys under electrochemical conditions via Metropolis Monte Carlo within an extended canonical ensemble. While Pd monomers are stable at all potentials considered, different extents of surface electrification are observed to promote the formation of Pd dimers and trimers, as well as clusters of Pd monomers. We find that the relative proportion of monomer, dimer, and trimer surface fractions is in good agreement with in situ scanning tunneling microscopy measurements. The further development and refinement of the approaches described herein may serve as a useful aid in the development of next-generation electrocatalysts.

Glycerol electrooxidation on Pd modified Au surfaces in alkaline media: Effect of the deposition method.

The catalytic effect of Pd on gold electrodes for glycerol oxidation is evaluated for Pd-Au surfaces prepared using three different methods: irreversible adsorption of palladium by a simple immersion of a gold electrode in palladium solution, the deposition of palladium on the gold substrate by a step potential from 1 to 0.75 V, and the forced deposition of palladium on the gold electrode with the help of a reducing hydrogen atmosphere. Voltammetry has been used for the electrochemical characterization of the Pd-Au deposits and to determine its reactivity towards glycerol oxidation, whereas FTIR experiments have allowed detecting adsorbed species and products formed during the oxidation reaction. Pd-Au surfaces prepared by irreversible adsorption are the electrodes that show the highest activity for the glycerol complete oxidation to carbonate, whereas Pd-Au surfaces made by the step potential are the catalyst that exhibits the highest rate for the formation and adsorption CO before carbonate production, poisoning the surface and diminishing their electrocatalytic properties. In addition to carbonate, glycerate, glycolate, and formate are detected as oxidation products. The integrated bands of the spectra are used to give quantitative information for comparing the product distribution of the different Pd-Au deposits prepared.

Controlling the Morphology of Au-Pd Heterodimer Nanoparticles by Surface Ligands.

Controlling the morphology of noble-metal nanoparticles is mandatory to tune specific properties such as catalytic and optical behavior. Heterodimers consisting of two noble metals have been synthesized, so far mostly in aqueous media using selective surfactants or chemical etching strategies. We report a facile synthesis for Au@Pd and Pd@Au heterodimer nanoparticles (NPs) with morphologies ranging from segregated domains (heteroparticles) to core-shell structures by applying a seed-mediated growth process with Au and Pd seed nanoparticles in 1-octadecene (ODE), which is a high-boiling organic solvent. The as-synthesized oleylamine (OAm) functionalized Au NPs led to the formation of OAm-Au@Pd heteroparticles with a "windmill" morphology, having an Au core and Pd "blades". The multiply twinned structure of the Au seed particles (⌀ ≈ 9-11 nm) is associated with a reduced barrier for heterogeneous nucleation. This leads to island growth of bimetallic Au@Pd heteroparticles with less-regular morphologies. The reaction process can be controlled by tuning the surface chemistry with organic ligands. Functionalization of Au NPs (Ø ≈ 9-11 nm) with 1-octadecanethiol (ODT) led to the formation of ODT-Au@Pd NPs with a closed Pd shell through a strong ligand-metal binding, which is accompanied by a redistribution of the electron density. Experiments with varied Pd content revealed surface epitaxial growth of Pd on Au. For OAm-Pd and ODT-Pd seed particles, faceted, Au-rich domain NPs and impeded core-shell NPs were obtained, respectively. This is related to the high surface energy of the small Pd seed particles (⌀ ≈ 5-7 nm). The metal distribution of all bimetallic NPs was analyzed by extended (aberration-corrected) transmission electron microscopy (HR-TEM, HAADF-STEM, EDX mapping, ED). The Au and Pd NPs, as well as the ODT-Au@Pd and OAm-Pd@Au heteroparticles, catalyze the reduction of 4-nitrophenol to 4-aminophenol with borohydride. The catalytic activity is dictated by the particle structure. OAm-Au@Pd heteroparticles with faceted Au domains had the highest activity because of a mixed Au-Pd surface structure, while ODT-Au@Pd NPs, where the active Au core is covered by a Pd shell, had the lowest activity.

Ethanol Decomposition on Pd–Au Alloy Catalysts

The mechanisms of ethanol (EtOH) decomposition via C–C or C–O bond cleavage on alloy surfaces are currently not well understood. In this study, we model EtOH decomposition on close-packed Pd–Au catalytic surfaces using density functional theory (DFT) calculations and derived Bronsted–Evans–Polanyi (BEP) relationships. Three characteristic Pd–Au surfaces are considered, Pd1Au2(111), Pd2Au1(111), and a Pd monolayer (ML), PdML(111), on a Au substrate. We show that, on close-packed Pd–Au surfaces, the C–C bond is easier to cleave than C–O, indicating that the formation of CH4 and CO is favored as the products of EtOH decomposition. Interestingly, we find that, though the C–C and C–O activation barriers on PdML(111) are generally lower than those on the other two surfaces, it is less active for EtOH decomposition due to a slow release of H2 and possible carbon coking. Pd2Au1(111), on the other hand, has a higher theoretical reaction rate due to facile H2 evolution from the surface and less carbon coking. A com...