Chemisorption of Hydrogen on Stepped Surfaces of Ni and Cu

Abstract

The chemisorption of hydrogen on stepped (410) surfaces of Ni and Cu has been studied using the embedded-atom method (EAM). First, contours of potential energy surface (PES) for atomic H on the stepped (410) surface of Ni, Cu are presented and compared with those of flat (100) surfaces. It is found that stepped surfaces have more active adsorption sites and the binding energy of H is larger at the step sites. Then, the dissociation of the hydrogen molecule on the stepped (410) surfaces of Ni and Cu is also investigated. The activation barrier Ea, adsorption heat qad and corresponding H–metal bond length R for different H2 dissociation pathways are calculated and the associated potential energy surfaces are obtained. The calculated results show that in the process of H2 approaching the concave site at the bottom of a step, the activation barrier for H2 dissociation is lowest; while for H2 approaching the outside edge of the terrace, the activation barrier is highest. Compared with that of H2 on perfect (100) surfaces of Ni, Cu, the presence of steps can significantly lower the activation barrier for dissociation of H2.