Promoting effect of AuCu alloying on Au-Cu/CeO2-catalyzed CO oxidation: A combined kinetic and in situ DRIFTS study

Reduced Au-Cu/CeO2 catalysts (Cu/Au = 1, 3) are more efficient towards the preferential oxidation of CO (PROX) than their calcined counter-parts. They exhibit lower activation energies and CO partial reaction orders (alpha(CO)), and even more interestingly, significantly higher O-2 partial reaction orders (beta(O2)). For the stoichiometric composition in particular (Au1Cu1/CeO2-R), the partial pressure of oxygen has a higher impact on the reaction rate than the partial pressure of CO (beta(O2) > alpha(CO)), which is unprecedented in low temperature catalysis involving gold and a reducible oxide support. DRIFTS studies further show (1) that Au1Cu1/CeO2-R contains electron-deficient, alloyed Cu atoms (Au-Cu+) and (2) that the formation of CO2 is enhanced by the preadsorption of O-2 rather than the preadsorption of CO. This suggests that CO oxidation proceeds via a Langmuir-Hinshelwood-type, bifunctional mechanism, involving CO adsorbed on Au-0 sites and oxygen adsorbed on electron-deficient, gold-alloyed copper sites. This alloy-mediated oxygen activation could be the key to the superior PROX activity of Au1Cu1/CeO2-R. (C) 2020 Elsevier Inc. All rights reserved.