SO 2 adsorption at room temperature on Ni(111) surface studied by XPS

The aim of this work was to investigate the initial stages of the SO 2 interaction with Ni(111) surfaces. SO 2 adsorption was performed at 1 × 10 −7 mbar, at room temperature, in a preparation chamber attached to the XPS analysis chamber. After each adsorption, the S 2p and O 1s core levels were analysed. Various S‐containing adsorbed species were observed: S(ads) located at 162.0 ± 0.2 eV, and SO 3 (ads) at 166.7 ± 0.2 eV. A weak signal at 163.8 ± 0.3 eV is tentatively assigned to a small amount of SO(ads). The data provided by the O 1s core level spectra have been used to confirm the nature of S‐containing adsorbed species. Changes in the surface concentrations of the different adspecies as a function of exposure indicate that, first, SO 2 dissociates into S(ads) and O(ads), then SO 2 can either dissociate or combine with the available O(ads) to form SO 3 (ads). The surface saturation is reached after 12 L.