Interaction of silica-supported small silver clusters with molecular oxygen. A computational study

The effect of nonbridging oxygen centers (NBOs) of a silica surface on the interaction of O2 with small Agn clusters (n = 3,4) has been studied computationally, using a scalar relativistic density functional method and embedding in an elastic polarizable environment described by molecular mechanics. Two types of O2 adsorption, molecular and dissociative, were analyzed. The electrostatic interaction of the metal clusters with the silica surface stabilizes adsorbed oxygen species, particularly those obtained via dissociative adsorption. O2 dissociation seems feasible on both silver clusters, Ag3 and Ag4, but relatively high activation barriers render O2 dissociation less probable than O2 desorption.