Photocatalytic Overall Water Splitting under Visible Light Using ATaO2N (A: Ca, Sr, Ba) and WO3 in a IO3‐/I‐ Shuttle Redox Mediated System.

Three mixed tantalum oxynitrides, ATaO2N (A = Ca, Sr, Ba), prepared by heating amorphous A2Ta2O7 under NH3, are applied in a two-step photoexcitation water-splitting system as a photocatalyst for H2 evolution. Platinum-loaded CaTaO2N and BaTaO2N are demonstrated to be active for H2 evolution in the presence of methanol or I− as an electron donor, whereas SrTaO2N is unable to produce H2 stably in the presence of I− due to self-oxidative decomposition accompanied by N2 production. The combination of Pt−CaTaO2N or Pt−BaTaO2N with Pt−WO3 achieves overall water splitting under visible irradiation. Pt−BaTaO2N is also demonstrated to be photoactive at wavelengths up to 660 nm, representing the first example of an overall water-splitting system in which visible light at wavelengths longer than 600 nm is effectively utilized for H2 evolution.