Interaction of H2S with high defect density TiO2(110) surfaces

The interaction of H2S with high defect density TiO2(110) surfaces has been studied by using ultraviolet and X-ray photoemission spectroscopy. Two distinct phases in the adsorption of H2S on this surface were observed. The first phase, which occurs at exposures ⩽ 1 L (1 L = 1 langmuir = 10−6 Torrs), was identified as dissociative adsorption of H2S; the second phase, which occurs for exposures ⩾ 1 L, is tentatively identified as molecular H2S adsorption. Subsequent exposure to O2 of the high defect density TiO2(110) surface that had been exposed to H2S indicated that the presence of the sulfur species produced by the adsorption of H2S significantly inhibits O2 adsorption. The decrease in the oxidation rate of high defect density TiO2(110) when exposed to O2 occurs despite the existence of a large amount of charge in the Tid states at EF. These results are discussed in the context of previously obtained data on the reaction of SO2 on both high defect density TiO2(110) and nearly perfect Ti2O3(101̄2) surfaces.