Influence of surface topology on NO adsorption:: NO on Ni(100) and Ni(510)

Abstract

The adsorption of NO on a flat Ni(100) surface and a stepped Ni(510) surface has been investigated using vibrational spectroscopy. At a substrate temperature of 100 K NO adsorbs associatively on both surfaces, notably in a strongly bent configuration at low NO coverages. The Ni(510) step sites are simultaneously populated with a specific adsorption state, of low N–O stretch energy, which decomposes already at 140 K. At high coverages NO adsorbs on top sites on both surfaces and the step sites of Ni(510) are populated with an adsorption state characterized by a N–O stretch energy close to the gas phase value. This comparison between NO adsorption on a flat and on a stepped nickel surface reveals a close correspondence between adsorption on Ni(100) and on the terraces of Ni(510), and that special step states exist involving a relatively weak N–O binding at low coverages and a relatively strong N–O binding at high coverages.