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Synergy and anti-synergy between palladium and gold in nanoparticles dispersed on a reducible support

Carter, James, Althahban, Sultan, Nowicka, Ewa, Freakley, Simon, Morgan, David John, Shah, Parag, Golunski, Stanislaw, Kiely, Christopher and Hutchings, Graham John 2016. Synergy and anti-synergy between palladium and gold in nanoparticles dispersed on a reducible support. ACS Catalysis 6 (10) , pp. 6623-6633. 10.1021/acscatal.6b01275

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Abstract

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.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Cardiff Catalysis Institute (CCI)
Chemistry
Subjects: Q Science > QD Chemistry
Uncontrolled Keywords: ceria−zirconia; CO oxidation; formic acid; gold; gold−palladium alloy; palladium; water-gas shift
Publisher: American Chemical Society
ISSN: 2155-5435
Funders: European Research Council
Date of First Compliant Deposit: 11 October 2016
Date of Acceptance: 29 August 2016
Last Modified: 24 Apr 2019 20:41
URI: http://orca.cf.ac.uk/id/eprint/95295

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