Reactivity of sulphur dioxide with Cu(100) surface investigated by infrared reflection absorption spectroscopy: role of structure and oxidation level

Interaction of sulphur dioxide (SO2) with the Cu(100) surface has been inve stigated by infrared reflection absorption spectroscopy (IRAS), Results hav e been compared with data obtained previously under similar conditions on t he Cu(110) surface in order to make clear the role of the surface structure on the adsorption process. Auger electron spectroscopy and XPS were used t o control the surface chemical state before and after SO2 interaction. On Cu(100), the dissociation of SO2 is observed for low exposure, and is th en followed by the formation of SOx molecular species (x greater than or eq ual to 2), On oxygen-induced reconstructed Cu(100), sulphites and sulphates are formed by interaction with SO2, Sulphites and sulphates are oxygen-bou nd to the surface, resulting from nucleophilic attack of the sulphur atoms of impinging SO2 molecules by the surface oxygen atoms. On the oxidized Cu( 100) surface, SO2 is only converted to sulphites, The less 'oxidizing' char acter of a superficial oxide layer compared to an oxygen adsorbed layer is correlated to the coordination and interatomic distances of the surface oxy gen atoms. The nature of the adsorbed species resulting from the interaction of SO2 wi th copper strongly depends on the structure and on the chemical composition of the surface. These data confirm that this molecule is a good probe of t he metallic and oxide surface reactivity, Copyright (C) 2000 John Wiley & S ons, Ltd.