Correlation of crystal and electronic structures with photophysical properties of water splitting photocatalysts InMO4 (M = V5+, Nb5+, Ta5+)

A novel series of visible light responding solid photocatalysts InMO4 (M = V, Nb, Ta) were synthesized by the solid-state reaction method, The InNbO4 and InTaO4 photocatalysts crystallize in the same crystal structure: wolframite-type, monoclinic with space group P2/c, while InVO4 belongs to the orthorhombic system with space group Cmcm. Under visible light irradiation (lambda > 420 nm), the native photocatalysts were found to evolve H, from pure water. The photocatalytic activity increases significantly by loading NiO as a co-catalyst. The bandgaps of InVO4, InNbO4 and InTaO4 were estimated to be 1.9, 2.5 and 2.6 eV respectively. The difference in the bandgaps of the photocatalysts is supposed to come from their different conduction band levels formed by V 3d in VO4, Nb 4d in NbO6, and Ta 5d in TaO6, resulting in different photocatalytic activities of the photocatalysts. (C) 2002 Elsevier Science B.V. All rights reserved.