(139f) Charging of Metal Oxide Supported Au Clusters and Its Effect On the CO Oxidation Reaction

Small Au clusters, when supported on defective MgO support, show enhanced catalytic activity towards the CO oxidation reaction. In the present work, we use first principle theoretical calculations to examine the effects of support defects on the electronic and structural characteristics of gold clusters along with their effect on the CO oxidation mechanism. It is found that an O vacancy on the support can effectively charge the clusters, with an electron flow from the support to the clusters. The adsorption energies of all the species involved in the CO oxidation reaction, such as the CO, O₂, O, CO₂, are calculated under different charge states of the clusters and in all possible binding sites. It is shown that the Au cluster's charge state significantly affects the binding strength of the adsorbents. For instance, molecular O₂ is found to weakly interact with neutral clusters and to chemisorb on negatively charged ones and activate CO. CO is found to preferentially interact with positively charged clusters. A CO₃ stable intermediate forms on Au clusters with specific structural and electronic characteristics. The reaction barriers of all elementary steps of the CO oxidation reaction mechanism are calculated. A complete microkinetic model is then constructed and the model results are compared to experimental data from the literature.