CHEMISORPTION OF HYDROGEN ON STEPPED(410) SURFACES OF NI AND CU

The chemisorption of hydrogen on stepped (410) in step notation, (s)-[4(100)X(010)] surfaces of Ni and Cu has been studied using the embedded-atom method (EAM). First, contours of the potential-energy surface (PES) for atomic H on stepped (410) surfaces of Ni, Cu are presented and compared with that of the 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 E(a), adsorption heat q(ad) and corresponding H-metal bond length R for different H-2, dissociation pathways are calculated and the associated potential-energy surfaces are obtained. The calculated results show that in the process of H-2 approaching the concave site at the bottom of a step, the activation barrier for H-2 dissociation is lowest; while for H-2 approaching the outside edge of the terrace, the activation barrier is highest. Compared with that of H-2 on perfect (100) surfaces of Ni, Cu, the presence of steps can significantly lower the activation barrier for dissociation of H-2.