Hydrogen on Pt0.5Ni0.5(110), alloying effects upon adsorption

Abstract Hydrogen adsorption on Pt 0.5 Ni 0.5 (110) was investigated by NRA, TPD, and Δφ measurements. The crystal surface was characterised by LEED and AES. No reconstruction of the surface was observed upon hydrogen exposure and the initial surface composition remains unaffected. At low temperatures and for hydrogen pressure higher than 10 −5 mbar, the saturation coverage was found to be close to one monolayer. Under these conditions, the adsorbed hydrogen gives rise to a +600 meV shift in the work function. Up to 0.1 in coverage the initial sticking coefficient ( S 0 ) is 0.1 and the heat of adsorption was found to be 70 kJ mol . These results are discussed in relation with the structure and composition of the surface and compared to known data for hydrogen adsorption on Ni(110). An interpretation based on the existence of two different adsorption sites is proposed.