Structure Sensitivity in CO Oxidation by a Single Au Atom Supported on Ceria

The mechanism of CO oxidation by a CeO 2 (110)-supported gold atom has been investigated by DFT calculations. A novel stable surface structure has been identified in which one surface O atom of ceria migrates toward the isolated Au atom, resulting in a surface Au–O species that can react with CO. After CO 2 desorption, the oxidation state of Au changes from positive to negative. In contrast to earlier explored CO oxidation mechanisms for single Au atoms on the CeO 2 (111) surface, O 2 can adsorb in the vacancy created in the CeO 2 (110) surface adjacent to Au. In essence, the difference in O 2 adsorption originates from the geometries of the two ceria terminations, pointing to strong structure sensitivity in the CO oxidation reaction. Dissociation of adsorbed O 2 heals the O vacancy and leaves an additional O atom on the surface. At this stage the Au atom is positively charged so that CO can adsorb followed by facile formation of CO 2 with the bridging O atom, closing the catalytic cycle. This mechanism successfully explains the role of surface O of ceria in CO oxidation by highly dispersed Au catalysts.