Effects of F for enhancement of H2 evolution on visible-light-driven photocatalyst of SrTiO3:Cr/Ta/F prepared by spray pyrolysis

Both anion (F−) and cation (Cr3+/Ta5+) doping were conducted simultaneously to prepare tri-doped photocatalyst, SrTiO3:Cr/Ta/F, by spray pyrolysis from aqueous precursor solutions. The ternary doping of F− ion into SrTiO3:Cr/Ta increased the hydrogen evolution rate up to 3887.9 μmol g−1 h−1 (quantum efficiency: 6.22%) under visible light irradiation, which was 1.84 times higher than that over SrTiO3:Cr/Ta. The optimum contents of dopants for the maximum hydrogen evolution rate were Cr (0.1 mol%), Ta (0.1 mol%) and F (6.0 mol%), respectively. The ternary doping of F− ion contributed to the reduction of Ti4+ and Cr6+ ions to Ti3+ and Cr3+ ions, respectively, by the generation of extra electrons in the lattice. The partially substituted structure of the photocatalyst could be expressed as Sr(Ti4+1−2x−zTi3+zCr3+x−yCr6+yTa5+x)(O2−3−wF−w).