Surface chemistry and interfacial charge-transfer mechanisms in photoinduced oxygen exchange at O_2-TiO_2 interfaces

摘要

Experimental results obtained over the last three decades on photoinduced oxygen isotopic exchange (POIE) of TiO_2 oxygen atoms with those of adsorbed water molecules and gaseous O_2 are analyzed in the light of recent information from the literature on the interaction of water and O _2 species with the TiO_2 surface (obtained by application of surface spectroscopy techniques in combination with high-resolution scanning tunnelling microscopy). The analysis emphasizes the singular role that bridging oxygen ions and bridging oxygen vacancies play in TiO_2 surface chemistry and interfacial electron transfer at the gas phase-TiO_2 interface in the absence and presence of water. The observed competition between POIE and the photo-oxidation (PO) of organic compounds is analyzed in terms of the recently developed direct-indirect (D-I) kinetic model for heterogeneous photocatalysis (D. Monllor-Satoca et al., Catal. Today, 2007, 129, 247, and references therein).