Reaction Mechanisms of CO Oxidation Catalyzed by Binary Copper Group Cluster Anions

Abstract

The detailed mechanisms of CO oxidation catalyzed by AuAg-,AuCu-,and AgCu-were investigated using density functional theory at the B3LYP level.The computational results indicate that the adsorption site of CO onto the mixed clusters decreases as follows:CuAuAg.Copper is the preferred adsorption site for O2 on the binary clusters.The adsorption of O2 onto gold was found to be the weakest.Three reaction pathways exist for CO oxidation catalyzed by AuAg-,AuCu-,and AgCu-.The most feasible pathway for CO oxidation catalyzed by AuAg-is CO insertion into the Ag―O bond of AuAgO-2 to produce the [Au―AgC(O―O)O]-intermediate,which then decomposes into CO2 and AuAgO-,or another CO molecule attacks [Au―AgC(O―O)O]-to form two CO2 molecules and AuAg-anion.A feasible pathway for CO oxidation catalyzed by AuCu-or AgCu-is initiated by the co-absorption of CO and O2 onto the clusters followed by the formation of a four-membered ring intermediate to produce the corresponding products.The cooperation effect of the second CO is very weak.The catalytic activities of AuAg-and AuCu-toward CO oxidation are stronger than that of Au-2.Doping the Au clusters with Ag and Cu increases the catalytic activity.These results are in agreement with the previous experimental results.