Optimum Particle Size for Gold-Catalyzed CO Oxidation

[Image: see text] The structure sensitivity of gold-catalyzed CO oxidation is presented by analyzing in detail the dependence of CO oxidation rate on particle size. Clusters with less than 14 gold atoms adopt a planar structure, whereas larger ones adopt a three-dimensional structure. The CO and O(2) adsorption properties depend strongly on particle structure and size. All of the reaction barriers relevant to CO oxidation display linear scaling relationships with CO and O(2) binding strengths as main reactivity descriptors. Planar and three-dimensional gold clusters exhibit different linear scaling relationship due to different surface topologies and different coordination numbers of the surface atoms. On the basis of these linear scaling relationships, first-principles microkinetics simulations were conducted to determine CO oxidation rates and possible rate-determining step of Au particles. Planar Au(9) and three-dimensional Au(79) clusters present the highest CO oxidation rates for planar and three-dimensional clusters, respectively. The planar Au(9) cluster is much more active than the optimum Au(79) cluster. A common feature of optimum CO oxidation performance is the intermediate binding strengths of CO and O(2), resulting in intermediate coverages of CO, O(2), and O. Both these optimum particles present lower performance than maximum Sabatier performance, indicating that there is sufficient room for improvement of gold catalysts for CO oxidation.