Two-step water splitting into H-2 and O-2 under visible light irradiation is examined combining Pt-ATaO(2)N (A = Ca, Sr, Ba) as a H-2 evolution photocatalyst and Pt-WO3 as an O-2 evolution photocat alyst by IO3-/I- shuttle redox-mediator. Overall water splitting proceeds when Pt-CaTaO2N or Pt-BaTaO2N is used for H, evolution photocatalyst, whereas photo-induced self-oxidative decomposition is predominant for Pt-SrTaO2N. The onset wavelengths of H-2 evolution almost accord with the absorption edges of CaTaO2N and BaTaO2N. The available wavelength of light for H, evolution in the present two-step water splitting system has been extended to 660 nm by using BaTaO2N. (c) 2007 Elsevier B.V. All rights reserved.