Photophysical and photocatalytic properties of InMO4 (M = Nb5+, Ta5+) under visible light irradiation

A new class of solid photocatalysts, InTaO4 and InNbO4, were prepared by the solid-state reaction. The powder X-ray diffraction and Rietveld structure refinement show that these compounds crystallize in the same crystal structure: wolframite type, monoclinic with space group P2/c. However, the octahedral TaO6 in InTaO4 slightly expands from that of NbO6 in InNbO4, leading to the longer lattice parameters in InTaO4. The photocatalytic H2 evolutions were obtained from pure water by the NiOx promoted InTaO4 and InNbO4 under visible light irradiation. The band gaps of InTaO4 and InNbO4 were estimated to be 2.6 and 2.5 eV, showing that the photocatalysts have ability to respond the wavelength of visible light region.