Photocatalytic Water Splitting for Hydrogen Production with Gd2MSbO7 (M = Fe, In, Y) Photocatalysts under Visible Light Irradiation

Novel photocatalysts Gd₂FeSbO₇, Gd₂InSbO₇ and Gd₂YSbO₇ were synthesized by the solid state reaction method for the first time. A comparative study about the structural and photocatalytic properties of Gd₂MSbO₇ (M = Fe, In, Y) was reported. The results showed that Gd₂FeSbO₇, Gd₂InSbO₇ and Gd₂YSbO₇ crystallized with the pyrochlore-type structure, cubic crystal system and space group Fd3m. The lattice parameter a for Gd₂FeSbO₇, Gd₂InSbO₇ or Gd₂YSbO₇ was 10.276026 Å, 10.449546 Å or 10.653651 Å. The band gap of Gd₂FeSbO₇, Gd₂InSbO₇ or Gd₂YSbO₇ was estimated to be 2.151 eV, 2.897 eV or 2.396 eV. For the photocatalytic water-splitting reaction, H₂ or O₂ evolution was observed from pure water with Gd₂FeSbO₇, Gd₂InSbO₇ or Gd₂YSbO₇ as catalyst under visible light irradiation (wavelength > 420 nm). Moreover, H₂ or O₂ also spilt by using Gd₂FeSbO₇, Gd₂InSbO₇ or Gd₂YSbO₇ as catalyst from CH₃OH/H₂O or AgNO₃/H₂O solutions under visible light irradiation (λ > 420 nm). Gd₂FeSbO₇ showed the highest activity compared with Gd₂InSbO₇ or Gd₂YSbO₇. At the same time, Gd₂InSbO₇ showed higher activity compared with Gd₂YSbO₇. The photocatalytic activities were further improved under visible light irradiation with Gd₂FeSbO₇, Gd₂InSbO₇ or Gd₂YSbO₇ being loaded by Pt, NiO or RuO₂. The effect of Pt was better than that of NiO or RuO₂ for improving the photocatalytic activity of Gd₂FeSbO₇, Gd₂InSbO₇ or Gd₂YSbO₇.