Tight-binding study of the adsorption of hydrogen on Pt, Au and Pt–Au (111) surfaces

Abstract

The results of a tight-binding study of the adsorption of hydrogen on Pt, Au and Pt–Au (111) surfaces using the Extended Hückel approximation are presented and discussed. It is shown that, in general, the bond between the adsorbed H atom and the Pt–Au alloy surface is weaker than that observed for pure metals. Therefore, the Pt-rich alloys can be catalytically more active than pure Pt because the weakening of the H–surface bond, due to the presence of inert Au atoms, makes the H atoms on the surface more mobile and more reactive with other adsorbed species. In pure Pt and pure Au, the top site is more stable than the bridge and hollow sites, while for Pt-rich and Au-rich alloys, the different sites show the same stability.