Photocatalytic water splitting is a challenging reaction because it is an ultimate solution to energy and environmental issues. Recently, many new powdered photocatalysts for water splitting have been developed. For example, a NiO (0.2 wt %)/NaTaO3:La (2 %) photocatalyst with a 4.1-eV band gap showed high activity for water splitting into H2 and O2 with an apparent quantum yield of 56 % at 270 nm. Overall water splitting under visible light irradiation has been achieved by construction of a Z-scheme photocatalysis system employing visible-light-driven photocatalysts, Ru/SrTiO3:Rh and BiVO4 for H2 and O2 evolution, and an Fe3+/Fe2+ redox couple as an electron relay. Moreover, highly efficient sulfide photocatalysts for solar hydrogen production in the presence of electron donors were developed by making solid solutions of ZnS with AgInS2 and CuInS2 of narrow band gap semiconductors. Thus, the database of powdered photocatalysts for water splitting has become plentiful.
Synthesis of New Visible Light Active Photocatalysts of Ba(In1/3Pb1/3M‘1/3)O3(M‘ = Nb, Ta): A Band Gap Engineering Strategy Based on Electronegativity of a Metal Component