Photocatalytic water splitting into H2 and/or O2 under UV and visible light irradiation with a semiconductor photocatalyst

We report three new series of solid photocatalysts with different crystal structure: Bi2MNbO7 (M = Al3+, Ga3+ and In3+); A(2)B(2)O(7) pyrochlore-type with cubic system and space group Fd3m; InMO4(M = Nb5+, Ta5+): ABO(4) wolframite-type with monoclinic system and space group P2/a and BiMO4(M = Nb5+, Ta5+): ABO(4) stibotantalite-type with triclinic system and space group PI(M = Ta) and orthorhombic systems with space group Pnna (M = Nb), respectively. Although the photocatalysts crystallize in the different crystal structure, they contain the same octahedral TaO6 and/or NbO6 in the different photocatalysts. The band structure of the photocatalysts is defined by Ta/Nb d-level and O 2p-level. The band gaps of the photocatalysts were estimated to be between 2.7 and 2.4 eV. Under visible light (lambda > 420 nm) or ultra-violet irradiation, these photocatalysts were found to split water into H-2 and/or O-2. The photocatalytic activity increases significantly by loading co-catalysts on the surface of the photocatalyst, such as NiO and Pt. (C) 2002 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.