Photocatalytic Water Splitting for Hydrogen Production with Novel Y₂MSbO₇ (M = Ga, In, Gd) under Visible Light Irradiation

Novel photocatalysts Y₂MSbO₇ (M = Ga, In, Gd) were synthesized by the solid state reaction method for the first time. A comparative study on the structural and photocatalytic properties of Y₂MSbO₇ (M = Ga, In, Gd) was reported. The results showed that Y₂GaSbO₇, Y₂InSbO₇ and Y₂GdSbO₇ crystallized with the pyrochlore-type structure, cubic crystal system, and space group Fd3m. The lattice parameter for Y₂GaSbO₇ was 10.17981 Å. The lattice parameter for Y₂InSbO₇ was 10.43213 Å. The lattice parameter for Y₂GdSbO₇ was 10.50704 Å. The band gap of Y₂GaSbO₇ was estimated to be 2.245 eV. The band gap of Y₂InSbO₇ was 2.618 eV. The band gap of Y₂GdSbO₇ was 2.437 eV. For the photocatalytic water-splitting reaction, H₂ or O₂ evolution was observed from pure water with Y₂GaSbO₇, Y₂InSbO₇ or Y₂GdSbO₇ as catalyst under visible light irradiation. (Wavelength > 420 nm). Furthermore, H₂ and O₂ were also evolved by using Y₂GaSbO₇, Y₂InSbO₇ or Y₂GdSbO₇ as a catalyst from CH₃OH/H₂O and AgNO₃/H₂O solutions, respectively, under visible light irradiation (λ > 420 nm). Y₂GaSbO₇ showed the highest activity compared with Y₂InSbO₇ or Y₂GdSbO₇. At the same time, Y₂InSbO₇ showed higher activity compared with Y₂GdSbO₇. The photocatalytic activities were further improved under visible light irradiation with Y₂GaSbO₇, Y₂InSbO₇ or Y₂GdSbO₇ 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 Y₂GaSbO₇, Y₂InSbO₇ or Y₂GdSbO₇.