Synergy between Pd and Au in a Pd–Au(100) bimetallic surface for the water gas shift reaction: a DFT study

Saqlain, Muhammad Adnan; Hussain, Akhtar; Siddiq, Muhammad; Leitão, Alexandre A.

doi:10.1039/c5ra07163a

Cited by 14 publications

(19 citation statements)

References 83 publications

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“…Consistent with the above cited literature, we have shown in previous work that a monolayer of Pd or Cu on Au (Pd–Au or Cu–Au bimetallic surface) forms a superior catalyst for CO oxidation . In the present work, we explore the potential application of the Cu–Au bimetallic surface for the WGSR.…”

Section: Introductionsupporting

confidence: 75%

“…Apart from the water dissociation reaction, the other main part of the WGSR consists of the oxidation of CO. This process is supposed to take place through three different mechanisms, namely through a direct redox reaction (R6), or via an intermediate formate (HCOO) or carboxyl (COOH) group (R7–10) . In the redox mechanism, a CO molecule is oxidized by an oxygen atom.…”

Section: Resultsmentioning

confidence: 99%

“…[63] Adsorbates such as CO, NO, and O 2 have also been shown to induce surfaces egregation in bimetallic structures. [37,[64][65][66][67][68][69] For example, EXAFS of Cu-Au/silica bimetallic nanoparticles has confirmed that when Cu-Au clusters are exposed to air,t he surface is enriched with Cu, whereas the Au preferably stays in the bulk. [61] However,avery recents tudy about Cu-Au bimetallics urfaces showed that in vacuum Cu prefers to stay in the bulk.…”

Section: Surfacemodelsmentioning

confidence: 99%

“…Consistent with the above cited literature, we have shown in previousw ork that am onolayer of Pd or Cu on Au (Pd-Au or Cu-Au bimetallic surface) forms as uperior catalyst for CO oxidation. [19,37] In the presentw ork, we explore the potential application of the Cu-Aubimetallic surface for the WGSR. However,t ou nderstand the role of the Cu in the bimetallic surface, similar calculations werep erformed on ap ure Cu(1 00)s urface.…”

Section: Introductionmentioning

confidence: 99%

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DFT Study of Synergistic Catalysis of the Water‐Gas‐Shift Reaction on Cu–Au Bimetallic Surfaces

et al. 2016

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The water‐gas‐shift reaction (WGSR) is an important industrial process that can be significantly enhanced at suitable catalyst surfaces. In this work, we investigate the catalytic behavior of metallic Cu(1 0 0) and bimetallic Cu–Au(1 0 0) surfaces. With density functional theory calculations, the variation in the Gibbs free energy (ΔG°), the activation barriers, and the rate constants for the WGSR are calculated. The variation in ΔG° for water dissociation shows that the process is spontaneous up to 520 K on the bimetallic surface and up to 229 K on the Cu(1 0 0) surface. The calculated rate constants for the process also show that the bimetallic surface is much more reactive than the Cu(1 0 0) surface. The calculated pressure–temperature phase diagram for water dissociation shows that the partial pressure of H2O required for water dissociation on the bimetallic surface is substantially lower than that on the Cu(1 0 0) surface at all the studied temperatures. Additionally, the calculations demonstrate that the kinetics of the water‐gas‐shift reaction is dominated by redox processes on both the surfaces.

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Section: Introductionsupporting

confidence: 75%

Section: Resultsmentioning

confidence: 99%

Section: Surfacemodelsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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DFT Study of Synergistic Catalysis of the Water‐Gas‐Shift Reaction on Cu–Au Bimetallic Surfaces

et al. 2016

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“…30 Saqlain et al. conducted a DFT study which predicted that Au and Pd should be highly active for the WGS reaction, due to the low energy barriers associated with H 2 O dissociation and CO oxidation, 31 but there have been no reported experimental studies to confirm this.…”

Section: Introductionmentioning

confidence: 99%

Synergy and Anti-Synergy between Palladium and Gold in Nanoparticles Dispersed on a Reducible Support

et al. 2016

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Highly active and stable bimetallic Au–Pd catalysts have been extensively studied for several liquid-phase oxidation reactions in recent years, but there are far fewer reports on the use of these catalysts for low-temperature gas-phase reactions. Here we initially established the presence of a synergistic effect in a range of bimetallic Au–Pd/CeZrO4 catalysts, by measuring their activity for selective oxidation of benzyl alcohol. The catalysts were then evaluated for low-temperature WGS, CO oxidation, and formic acid decomposition, all of which are believed to be mechanistically related. A strong anti-synergy between Au and Pd was observed for these reactions, whereby the introduction of Pd to a monometallic Au catalyst resulted in a significant decrease in catalytic activity. Furthermore, monometallic Pd was more active than Pd-rich bimetallic catalysts. The nature of the anti-synergy was probed by several ex situ techniques, which all indicated a growth in metal nanoparticle size with Pd addition. However, the most definitive information was provided by in situ CO-DRIFTS, in which CO adsorption associated with interfacial sites was found to vary with the molar ratio of the metals and could be correlated with the catalytic activity of each reaction. As a similar correlation was observed between activity and the presence of Au0* (as detected by XPS), it is proposed that peripheral Au0* species form part of the active centers in the most active catalysts for the three gas-phase reactions. In contrast, the active sites for the selective oxidation of benzyl alcohol are generally thought to be electronically modified gold atoms at the surface of the nanoparticles.

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Catalytic Hydrogen Production by Janus CuAg Nanostructures

et al. 2018

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Janus nanostructures comprising intimate interfaces can integrate distinct building blocks into a single unit and generate new synergetic effects and desirable functionality through the interfaces. Herein, we report a wet‐chemistry approach mediated by n‐butylamine to directly create heterogeneous CuAg nanoparticles (NPs). Such newly created heterostructures with unique interfaces between the Cu and Ag domains exhibit superior catalytic performance for the water‐gas shift (WGS) reaction to produce hydrogen (H2). By optimizing the composition of the heterogeneous CuAg NPs, the supports, as well as the reaction parameters, the CuAg NPs/ZnO can deliver a TOF value of 673.5 h−1 and a 198.1 μmol yield of H2, significantly outperforming Cu NPs, Ag NPs, mixed Cu/Ag NPs, as well as CuAg NPs without an interface. XPS analysis indicates that the excellent performance is attributed to a unique interface effect, which endows the optimized catalyst with an enhanced antioxidant ability and thus large ratio of metallic Cu. The catalyst also shows outstanding durability with a largely maintained interface and activity after nine runs.

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Synergy between Pd and Au in a Pd–Au(100) bimetallic surface for the water gas shift reaction: a DFT study

Abstract: Density functional theory calculations were performed to model a reaction relevant bimetallic surface and study the water gas shift reaction.

Cited by 14 publications

References 83 publications

DFT Study of Synergistic Catalysis of the Water‐Gas‐Shift Reaction on Cu–Au Bimetallic Surfaces

DFT Study of Synergistic Catalysis of the Water‐Gas‐Shift Reaction on Cu–Au Bimetallic Surfaces

Synergy and Anti-Synergy between Palladium and Gold in Nanoparticles Dispersed on a Reducible Support

Catalytic Hydrogen Production by Janus CuAg Nanostructures

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