Influence of charge state and active site structure of tetrahedral copper and silver clusters on the methane activation

Abstract

Abstract The process of methane activation on tetrahedral Cu20 and Ag20 clusters was investigated by the density functional theory. In particular, the influence of charge state and structure of clusters on the process of adsorption and dissociation of CH4 molecule was considered. Both neutral and cationic copper clusters were found to promote methane activation better than silver clusters. The study has shown that the coordination number of a metal atom corresponding to the active site has a significant impact on the value of activation energy of methane dissociation. The process of CH4 adsorption is more favorable on the vertex atoms, while C H bond rupture occurs on the edge atoms of the cluster. The presence of a positive charge leads to a significant increase in the value of adsorption energy on the vertex atoms and a decrease in the activation barrier of methane dissociation on the edge sites.