Chemical structure of photocatalytic active sites in nanosize TiO 2

Abstract

Nanosize TiO 2 has been widely used in photocatalysis. However, works on speciation of photocatalytic active sites in nanosize TiO 2 is still lacking in the literature. Hence, the main objective of this work was to study chemical structure of photoactive species in the nanosize TiO 2 (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 A 1 (4969.4 eV), A 2 (4970.5 eV) and A 3 (4972.3 eV) in the TiO 2 photocatalysts can be attributed to 1s–3d transitions for four- (TiO 4), five- ((Ti O)O 4), and six- (TiO 6) coordinated Ti structural species, respectively. The A 2 species on the surfaces of the nanosize TiO 2 was found to be the main active sites during photocatalytic degradation of methylene blue.