Photocatalysis and solar hydrogen production*
Akihiko Kudo1,2
1Department of Applied Chemistry, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan; 2Core Research for Evolutional Science and Technology, Japan Science and Technology Agency (CREST, JST), 4-1-8 Honcho, Kawaguchi-shi, Saitama 332-001, Japan
Abstract: 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.
Keywords: Photocatalysts; water splitting; solar light; hydrogen; metal oxides; metal sulfides.
*Pure Appl. Chem. 79, 1831-2100. An issue of reviews and research papers based on lectures presented at the 1st International IUPAC Conference on Green-Sustainable Chemistry, held in Dresden, Germany, 10-15 September 2006.