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

The synergic effect of cation doping and phase composition for the further improvement of the photocatalytic activity of TiO 2 under visible light is reported for the first time. Fe 3   + and Sn 4   + co-doped TiO 2 with optimized phase composition were synthesized through a simple soft-chemical solution method. The visible-light-driven photocatalytic activity of Fe 3   + and Sn 4   + co-doped TiO 2 was 5 times of that of Evonik P25 TiO 2 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, 119 Sn Mössbauer spectroscopy, and X-ray absorption fine structure spectroscopy. It is indicated that Sn 4   + 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 Sn 4   + doped into the lattice. Furthermore, the doping of Sn 4   + into TiO 2 lattice can stabilize the phase composition when Fe 3   + is co-doped. In the Fe 3   + and Sn 4   + co-doped TiO 2 , Sn 4   + is mainly used to tune and stabilize the phase composition of TiO 2 and Fe 3   + acts as a doping cation to narrow the band gap of TiO 2 . Both band gap and phase composition of TiO 2 can be tuned effectively by the simultaneous introduction of Fe 3   + and Sn 4   + . 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 TiO 2 under visible light.