抄録
Photo-activated electrons reduce reactants and photo-generated positive holes oxidize reactants in photocatalysis. The electrons and holes, however, mostly or partly recombine before used for the reactions because photocatalyst particles are basically symmetry, and thereby can not generate effective electric field to separate electrons and holes. Both the reduction and the oxidation proceed in the same space simultaneously in conventional photocatalysis reactors using suspended or supported catalyst particles, and thereby reduced products tend to be oxidized and oxidized products to be reduced. These reverse reactions and the infertile recombination of electrons and holes lower photon-efficiency of photocatalysis. In an effort for preventing the reverse reactions and the recombination to raise photon- efficiency, the authors fabricated a reactor equipped with a hetero-sided photocatalyst plate supporting an oxidation photocatalyst at one surface of a conductive metal plate and reduction catalyst at the other surface of the metal plate. The hetero-sided photocatalyst plate can generate the effective electric field to drive electrons and holes opposite directions due to its asymmetrical structure and the Schottky potential generated at the interface between the reactant solution and the photocatalyst. The plate divides the reactor volume into two spaces, oxidation and reduction spaces. The divided reactor equipped with the hetero-sided photocatalyst plate achieved a high photon-efficiency, five times as large as the undivided reactor, when hydrogen was generated at 20% photon-efficiency (the external quantum yield) from acidic water in the reduction space while formic acid was oxidized in the oxidation space.
