Strategies for the Development of Visible-light-driven Photocatalysts for Water Splitting

Photocatalysts for water splitting developed by the present authors are reviewed. A NiO (0.2 wt%)/NaTaO 3 :La (2%) photocatalyst with a 4.1-eV band gap showed high activity for water splitting into H 2 and O 2 with an apparent quantum yield of 56% at 270nm. Many visible-light-driven photocatalysts have also been developed through band engineering by doping of metal cations, forming new valence bands with Bi 6 s , Sn 5 s , and Ag 4 d orbitals, and by making solid solutions between ZnS with wide band gap and narrow band gap semiconductors. Overall water splitting under visible light irradiation has been achieved by construction of a Z-scheme photocatalysis system employing the visible-light-driven photocatalysts for H 2 and O 2 evolution, and the Fe 3 + /Fe 2 + redox couple as an electron relay.