Dissociation of molecular oxygen on unpromoted and cesium promoted Ag(110) surfaces

We have computed the binding energies for the molecular and atomic chemisorbed states of oxygen, and barriers between them, for a three-layer model cluster representative of the (110) face of silver as a function of cesium coverage. To increase computational efficiency, a one-electron potential was developed for the third layer of the silver atoms making up the model cluster. These calculations predict a barrier of ∼17 kcal/mol to dissociate chemisorbed O2, in good agreement with experiment. When a Cs atom is added to the cluster, the barrier for O2 dissociation is significantly lowered. However, when two Cs atoms were added the barrier for dissociation increased relative to the barrier for the cluster with one adsorbed Cs atom. These calculations predict that the dissociation of chemisorbed molecular oxygen will have a Cs coverage dependence. This dissociation pattern is consistent with prior calculations on Ag(111) model clusters.