Interaction of deuterium with well-defined PtxRu1-x/Ru(0001) surface alloys

The adsorption and desorption of deuterium on structurally well-characterized, pseudomorphic PtxRu1-x surface alloys on a Ru(0001) substrate was investigated by temperature programmed desorption. The interaction of deuterium with these surface alloys, which, based on previous high resolution scanning tunneling microscopy measurements, have a nearly random distribution of the surface atoms, is markedly altered compared to that with the pure components, Ru(0001) and Pt(111). With increasing Pt surface content, the onset of D-2 desorption shifts to lower temperature, leading to a significant broadening of the spectra and finally to a pronounced low-temperature peak at 145 K. The low-temperature state becomes dominant at Pt concentrations close to 100% and is assigned to deuterium desorption from a Ru(0001) supported Pt monolayer film. The characteristic changes in the deuterium desorption behavior induced by Pt surface. atoms are discussed in a picture involving geometric ensemble effects as well as electronic strain effects and ligand effects and are compared with results of recent density functional calculations and results on the interaction of CO with similar surfaces.