Photocatalytic Water Splitting into H2 and O2 over R3TaO7 and R3NbO7 (R = Y, Yb, Gd, La): Effect of Crystal Structure on Photocatalytic Activity

The photocatalytic activities of R 3 TaO 7 and R 3 NbO 7 (R = rare earth Y, Yb, Gd, or La) were strongly dependent on the crystal structure. Photocatalytic splitting of pure water into H 2 and O 2 proceeded over NiO x -loaded La 3 TaO 7 and La 3 NbO 7 photocatalysts with weberite-orthorhombic structure, while only a small amount of H 2 was evolved over other photocatalysts with cubic structure. In the case of the La 3 TaO 7 and La 3 NbO 7 photocatalyst, the phase transition from cubic into orthorhombic was observed at 1000−1050 °C, and the photocatalytic activity was drastically increased by phase transition from cubic into orthorhombic.