Atomic oxygen adsorption on Au (100) and bimetallic Au/M (M=Pt and Cu) surfaces

Jalili, Seifollah; Isfahani, Asghar Zeini; Habibpour, Razieh

doi:10.1016/j.comptc.2012.02.033

Cited by 15 publications

(10 citation statements)

References 29 publications

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“…A previous DFT study showed that Pd prefers to substitute top-layered Cu and the authors employed Pd/Cu(111) models with varied surface coverages of Pd to represent the Pd-Cu bimetallic catalysts . Some other computational studies with M/Cu (M = Pd, Au) catalysts used a similar approach to construct the bimetallic models. , To elucidate the effect of surface segregation of Pd-Cu catalysts on CO 2 hydrogenation, we constructed a Pd-Cu bimetallic model based on Cu(111) and replaced the Cu atoms on the topmost layer by a monolayer (ML) of Pd atoms, denoted as 1 ML Pd/Cu(111), on which the adsorption of H 2 and CO 2 as well as initial hydrogenation of CO 2 to HCOO* and COOH* were examined. Relevant results are provided in Figures S3 and S4.…”

Section: Resultsmentioning

confidence: 99%

Mechanistic Understanding of Alloy Effect and Water Promotion for Pd-Cu Bimetallic Catalysts in CO₂ Hydrogenation to Methanol

et al. 2018

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Density functional theory (DFT) calculations on Pd-Cu bimetallic catalysts reveal that the stepped PdCu(111) surface with coordinatively unsaturated Pd atoms exposed on the top is superior for CO 2 and H 2 activation and for CO 2 hydrogenation to methanol in comparison to the flat Cu-rich PdCu 3 (111) surface. The energetically preferred path for CO 2 to CH 3 OH over PdCu(111) proceeds through CO 2 * → HCOO* → HCOOH* → H 2 COOH* → CH 2 O* → CH 3 O* → CH 3 OH*. CO formation from CO 2 via a reverse water-gas shift (RWGS) proceeds more quickly than CH 3 OH formation in terms of kinetic calculations, in line with experimental observation. A small amount of water, which is produced in situ from both RWGS and CH 3 OH formation, can accelerate CO 2 conversion to methanol by reducing the kinetic barriers for O−H bond formation steps and enhancing the TOF. Water participation in the reaction alters the rate-limiting step according to the degree of rate control (DRC) analysis. In comparison to CO 2 , CO hydrogenation to methanol on PdCu(111) encounters higher barriers and thus is slower in kinetics. Complementary to the DFT results, CO 2 hydrogenation experiments over SiO 2 -supported bimetallic catalysts show that the Pd-Cu(0.50) that is rich in a PdCu alloy phase is more selective to methanol than the PdCu 3 -rich Pd-Cu(0.25). Moreover, advanced CH 3 OH selectivity is also evidenced on Pd-Cu(0.50) at a specific water vapor concentration (0.03 mol %), whereas that of Pd-Cu(0.25) is not comparable. The present work clearly shows that the PdCu alloy surface structure has a major effect on the reaction pathway, and the presence of water can substantially influence the kinetics in CO 2 hydrogenation to methanol.

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Section: Resultsmentioning

confidence: 99%

Mechanistic Understanding of Alloy Effect and Water Promotion for Pd-Cu Bimetallic Catalysts in CO₂ Hydrogenation to Methanol

et al. 2018

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“…Atomic oxygen prefers the threefold fcc site on Au(111), the fourfold hollow site on Au(100), and the twofold bridge site on the step edge of Au(211), with BEs of −2.41 eV (−2.43 eV), −2.69 eV(−2.85 eV), and −2.80 eV(−2.83 eV), respectively. Hydroxyl prefers to adsorb in a top‐tilted configuration on the bridge sites of all three Au facets with BEs of −1.36 eV (−1.47 eV), −1.96 eV, and −2.07 eV on Au(111), Au(100), and Au(211), respectively.…”

Section: Resultsmentioning

confidence: 99%

Formic acid decomposition on Au catalysts: DFT, microkinetic modeling, and reaction kinetics experiments

et al. 2014

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A combined theoretical and experimental approach is presented that uses a comprehensive mean‐field microkinetic model, reaction kinetics experiments, and scanning transmission electron microscopy imaging to unravel the reaction mechanism and provide insights into the nature of active sites for formic acid (HCOOH) decomposition on Au/SiC catalysts. All input parameters for the microkinetic model are derived from periodic, self‐consistent, generalized gradient approximation (GGA‐PW91) density functional theory calculations on the Au(111), Au(100), and Au(211) surfaces and are subsequently adjusted to describe the experimental HCOOH decomposition rate and selectivity data. It is shown that the HCOOH decomposition follows the formate (HCOO) mediated path, with 100% selectivity toward the dehydrogenation products (CO2 + H2) under all reaction conditions. An analysis of the kinetic parameters suggests that an Au surface in which the coordination number of surface Au atoms is ≤4 may provide a better model for the active site of HCOOH decomposition on these specific supported Au catalysts. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1303–1319, 2014

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“…Oxygen adsorption has been found to favor hollow sites, ,, and therefore, the γ 1 phase is assigned to O chemisorbed in 4-fold hollows. This differs from the studies conducted on O/Au(110)-1 × 2, where the γ 1 state was assigned to a surface oxide, which was disputed after O/Au(111) studies, in which both γ 1 and γ 2 phases were assigned as oxygen species present on the surface. , Additionally, upon dissociating O 2 over a hot filament to induce chemisorbed atomic oxygen (and the lifting of the hex-reconstruction) on Au(100), one O 2 desorption peak was observed at 470 K, in good agreement with the position of the γ 1 peak in Figure A, at 460 K. This supports our argument that γ 1 oxygen is chemisorbed oxygen rather than gold oxide.…”

Section: Resultsmentioning

confidence: 99%

Reactivity and Morphology of Oxygen-Modified Au Surfaces

Baber¹,

Torres²,

Müller

et al. 2012

J. Phys. Chem. C

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Inducing the adsorption of oxygen on gold surfaces transforms the inert metal into a surprisingly reactive material, which acts as a highly selective, low-temperature catalyst. The strong interaction of atomic oxygen with Au greatly affects the surface morphology by increasing the number of undercoordinated Au atoms and lifting the surface reconstruction. Through the combination of experimental and theoretical techniques, we have fully characterized an oxygenmodified Au(100) surface and determined the structure− reactivity relationship of O−Au species. Bulk-implanted oxygen does not affect the reactivity of Au surfaces and subsurface oxygen is found to be unstable. Oxygen stabilizes undercoordinated Au atoms on the surface and becomes highly active for oxidation reactions when adsorbed on unreconstructed Au(100) sites.

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Atomic oxygen adsorption on Au (100) and bimetallic Au/M (M=Pt and Cu) surfaces

Cited by 15 publications

References 29 publications

Mechanistic Understanding of Alloy Effect and Water Promotion for Pd-Cu Bimetallic Catalysts in CO₂ Hydrogenation to Methanol

Mechanistic Understanding of Alloy Effect and Water Promotion for Pd-Cu Bimetallic Catalysts in CO₂ Hydrogenation to Methanol

Formic acid decomposition on Au catalysts: DFT, microkinetic modeling, and reaction kinetics experiments

Reactivity and Morphology of Oxygen-Modified Au Surfaces

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Atomic oxygen adsorption on Au (100) and bimetallic Au/M (M=Pt and Cu) surfaces

Cited by 15 publications

References 29 publications

Mechanistic Understanding of Alloy Effect and Water Promotion for Pd-Cu Bimetallic Catalysts in CO2 Hydrogenation to Methanol

Mechanistic Understanding of Alloy Effect and Water Promotion for Pd-Cu Bimetallic Catalysts in CO2 Hydrogenation to Methanol

Formic acid decomposition on Au catalysts: DFT, microkinetic modeling, and reaction kinetics experiments

Reactivity and Morphology of Oxygen-Modified Au Surfaces

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Product

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Mechanistic Understanding of Alloy Effect and Water Promotion for Pd-Cu Bimetallic Catalysts in CO₂ Hydrogenation to Methanol

Mechanistic Understanding of Alloy Effect and Water Promotion for Pd-Cu Bimetallic Catalysts in CO₂ Hydrogenation to Methanol