SO2 adsorption on Pt(111): HREELS, XPS and UPS study

Abstract The chemistry of SO 2 on Pt(111) has been studied by X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), temperature programmed desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS). At 100 K, SO 2 adsorbs molecularly through the S and one O atom. Photoemission results indicate that significant charge transfer occurs between the Pt d-band and the lowest unoccupied molecular orbital of SO 2 . Molecular orbital analysis reveals that atop and two-fold sites are energetically feasible for SO 2 adsorption, but two-fold sites are more favorable. Upon heating to 300 K, SO 2 molecules undergo desorption and dissociation. The latter leads to adsorbed S, SO and SO 4 . An SO 2 lattice vibration mode was observed by HREELS when an SO 2 multilayer was dosed at 100 K; and it was enhanced when SO 2 was dosed at 110 K. There is a resonance in this feature as the incident electron energy is varied, which implies that a nondipolar scattering process contributes. Multilayer SO 2 , formed upon adsorption at 100 K, is metastable.