Hydrogen production with Ga2BiSbO7, Fe2BiSbO7 and Gd2BiSbO7 as photocatalysts under visible light irradiation

M2BiSbO7 (M = Ga, Fe, Gd) were synthesized by solid state reaction process for the first time as novel photocatalysts. The structural and photocatalytic properties of M2BiSbO7 (M = Ga, Fe, Gd) were reported. The results showed that Ga2BiSbO7, Fe2BiSbO7 and Gd2BiSbO7 crystallized with the pyrochlore-type structure, cubic crystal system and space group Fd3m. The lattice parameter for Ga2BiSbO7, Fe2BiSbO7 or Gd2BiSbO7 was 10.34804 Å, 10.41030 Å or 10.70353 Å respectively. In addition, the band gaps of Ga2BiSbO7 and Gd2BiSbO7 were separately estimated to be 1.955 eV and 2.081 eV. For the photocatalytic water splitting reaction, H2 or O2 evolved abundantly with Ga2BiSbO7, Fe2BiSbO7 or Gd2BiSbO7 as photocatalyst from CH3OH/H2O or AgNO3/H2O solution respectively under visible light irradiation (Wavelength > 420 nm). The results indicated that the activities of three photocatalysts followed the order of Ga2BiSbO7 > Fe2BiSbO7 > Gd2BiSbO7. Moreover, photocatalytic H2 evolution from aqueous methanol solution was observed with Ga2BiSbO7, Fe2BiSbO7 or Gd2BiSbO7 as photocatalyst under different light irradiation (λ > 390 nm and λ > 0 nm). The results showed that the photocatalytic activity decreased with increasing incident wavelength (λ). The photocatalytic activity was further enhanced under visible light irradiation with Ga2BiSbO7, Fe2BiSbO7 or Gd2BiSbO7 loaded by Pt, NiO or RuO2 (λ > 420 nm). The effect of Pt was better than that of NiO or RuO2 for improving the photocatalytic activity of Ga2BiSbO7, Fe2BiSbO7 or Gd2BiSbO7.