The adsorption of molecular sulfur on TiO2(110)(1x1) was studied with scanning tunnelling microscopy and photo-electron spectroscopy. At room temperature S bonded dissociatively to 5-fold coordinated Ti atoms and oxygen vacancies. At elevated temperatures (120 to 440C) sulfur replaced surface oxygen atoms. Evidence was found that the reduction state of TiO2 crystals strongly affects the surface coverage of S at elevated temperatures. The rate of the O-S site exchange was kinetically limited by the arrival of diffusing bulk defects at the surface.

Bulk-Defect Dependent Adsorption on a Metal Oxide Surface: S/TiO2(110). Hebenstreit, E.L.D., Hebenstreit, W., Geisler, H., Ventrice, C.A., Sprunger, P.T., Diebold, U.: Surface Science, 2001, 486[3], L467-74