SO2 adsorption at room temperature on Ni(111) surface studied by XPS

The aim of this work was to investigate the initial stages of the SO2 interaction with Ni(111) surfaces. SO2 adsorption was performed at 1 x 10(-7) mbar, at room temperature, in a preparation chamber attached to the XPS analysis chamber. After each adsorption, the S 2p and O is core levels were analysed. Various S-containing adsorbed species were observed: S(ads) located at 162.0 +/- 0.2 eV, and SO3 (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, SO2 dissociates into S(ads) and O(ads), then SO2 can either dissociate or combine with the available O(ads) to form SO3 (ads). The surface saturation is reached after 12 L. Copyright (C) 2004 John Wiley Sons, Ltd.