Synergic effect of cation doping and phase composition on the photocatalytic performance of TiO2 under visible light

Abstract

The synergic effect of cation doping and phase composition for the further improvement of the photocatalytic activity of TiO2 under visible light is reported for the first time. Fe3+ and Sn4+ co-doped TiO2 with optimized phase composition were synthesized through a simple soft-chemical solution method. The visible-light-driven photocatalytic activity of Fe3+ and Sn4+ co-doped TiO2 was 5 times of that of Evonik P25 TiO2 using degradation of methylene blue as model reaction. The synthesized photocatalysts were characterized by powder X-ray diffraction, UV–Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, 119Sn Mössbauer spectroscopy, and X-ray absorption fine structure spectroscopy. It is indicated that Sn4+ doping can facilitate the phase transition from anatase to rutile. The different ratios of anatase and rutile can be achieved by tuning the amount of Sn4+ doped into the lattice. Furthermore, the doping of Sn4+ into TiO2 lattice can stabilize the phase composition when Fe3+ is co-doped. In the Fe3+ and Sn4+ co-doped TiO2, Sn4+ is mainly used to tune and stabilize the phase composition of TiO2 and Fe3+ acts as a doping cation to narrow the band gap of TiO2. Both band gap and phase composition of TiO2 can be tuned effectively by the simultaneous introduction of Fe3+ and Sn4+. The synergic effect of optimized phase composition (anatase/rutile=25/75) and narrowed band gap should be the two main reasons for the promoted photocatalytic activity of TiO2 under visible light.