Chemical structure of photocatalytic active sites in nanosize TiO2 Original Research Article

Nanosize TiO2 has been widely used in photocatalysis. However, works on speciation of photocatalytic active sites in nanosize TiO2 is still lacking in the literature. Hence, the main objective of this work was to study chemical structure of photoactive species in the nanosize TiO2 (synthesized by sol–gel method) by X-ray absorption near edge structural (XANES) spectroscopy. The refined pre-edge XANES spectra show that photocatalytic active species such as A1 (4969.4 eV), A2 (4970.5 eV) and A3 (4972.3 eV) in the TiO2 photocatalysts can be attributed to 1s–3d transitions for four- (TiO4), five- ((Tidouble bond; length as m-dashO)O4), and six- (TiO6) coordinated Ti structural species, respectively. The A2 species on the surfaces of the nanosize TiO2 was found to be the main active sites during photocatalytic degradation of methylene blue.