Co-doping schemes to enhance H2 evolution under visible light irradiation over SrTiO3:Ni/M (M = La or Ta) prepared by spray pyrolysis

Two photocatalysts, SrTiO3:Ni/La and SrTiO3:Ni/Ta, were prepared by continuous spray pyrolysis. The effects of the co-dopants on hydrogen evolution over the uncalcined photocatalysts were evaluated under visible light irradiation. The co-doping of La3+ into SrTiO3:Ni transformed the charge structure and increased the presence of Ni2+ at the expense of Ni3+ in the host lattice structure. The co-doping of Ta5+ into SrTiO3:Ni also increased the Ni2+/Ni3+ ratio around the Ti4+ ions. Compared with SrTiO3:Ni, SrTiO3:Ni/La showed a 3 times greater rate of hydrogen evolution under visible light irradiation and SrTiO3:Ni/Ta, a 4 times greater rate. The co-doping levels required for optimized hydrogen evolution over SrTiO3:Ni/La and SrTiO3:Ni/Ta prepared by spray pyrolysis were smaller than those prepared by other methods. Spray pyrolysis also produced particles with large surface areas and high roughnesses.