Two step water splitting into H2 and O2 under visible light by ATaO2N (A = Ca, Sr, Ba) and WO3 with shuttle redox mediator

Two-step water splitting into H2 and O2 under visible light irradiation is examined combining Pt–ATaO2N (A = Ca, Sr, Ba) as a H2 evolution photocatalyst and Pt–WO3 as an O2 evolution photocatalyst by IO 3 - / I - shuttle redox-mediator. Overall water splitting proceeds when Pt–CaTaO2N or Pt–BaTaO2N is used for H2 evolution photocatalyst, whereas photo-induced self-oxidative decomposition is predominant for Pt–SrTaO2N. The onset wavelengths of H2 evolution almost accord with the absorption edges of CaTaO2N and BaTaO2N. The available wavelength of light for H2 evolution in the present two-step water splitting system has been extended to 660 nm by using BaTaO2N.