Water Splitting Reaction under Visible Light Using Artificial Photosynthesis-photocatalyst System.

Abstract

H2O splitting into H2 and O2 with 2 different semiconductor photocatalysts and a redox mediator, mimicking the Z-scheme mechanism of photosynthesis, is discussed. The H2 evolution occurs on a Pt-SrTiO3 (Cr,Ta-doped) photocatalyst using an I- electron donor during visible light irradn. A Pt-WO3 photocatalyst had excellent activity for O2 evolution using an IO3- electron acceptor under visible light. Both H2 and O2 evolution was obsd. with a stoichiometric ratio, H2/O2 = 2 for >250 h operation with visible light using a mixt. of the Pt-WO3 and the Pt-SrTiO3(Cr-Ta-doped) powders suspended in an aq. NaI soln. It is the 1st result for stoichiometric H2O splitting using oxide semiconductor photocatalysts and visible light. A two-step photoexcitation mechanism, with the I-/IO3- couple as redox mediator, is proposed. The quantum efficiency of stoichiometric H2O splitting was ∼0.1% at 420.7 nm. [on SciFinder(R)]