Hydrogen adsorption on the Pt(111)(3 × 3)R30°-Sn surface alloy studied by high resolution core level photoelectron spectroscopy O

Investigation of the clean and atomic hydrogen covered Pt(111)(3 × 3)R30°-Sn surface alloy has been carried out using high resolution core level photoelectron spectroscopy. The Pt 4f72 spectrum recorded from the clean surface alloy shows a single surface peak shifted −0.25 eV relative to the bulk. Its interpretation by means of a thermodynamical model using Born-Haber cycles confirms the surface alloy model. Adsorption of H does not change the line shape of the Sn 4d core level while a new surface component shifted by 0.59 eV compared to the bulk peak appears in the Pt 4f72 spectrum. These results are discussed in the light of the thermodynamical calculations. H atoms are believed to bind only to Pt atoms, and their adsorption site seems to be influenced by the tin present in the surface layer.