Dye-Sensitizer Effects on a Pt/KTa(Zr)O3 Catalyst for the Photocatalytic Splitting of Water

摘要

The development of an active catalyst for the photocatalytic decomposition of pure water into H2 and O2 is urgently required from an energy-saving viewpoint. Various semiconductor oxides, mainly TiO2- and Nb-based mixed oxides, have been investigated for this reaction. Recently, however, various Ta-based oxides reported by Kato and Kudo et al. have attracted interest as new photocatalytic materials because of their fairly high activity for the photocatalytic splitting of H2O. In addition, Zou et al. have found that Ni-doped InTaO4 can decompose H2O upon activation with visible light, as can the mixed SrTiO3/WO3 compound reported by Sayama et al. In a previous study we found that Zr-doped KTaO3 exhibits a high activity, splitting H2O into almost stoichiometric amounts of H2 and O2. However, these photocatalysts mainly consist of oxide semiconductors combined with a metal or metal oxide such as Pt or NiO. On the other hand, dye-sensitized solar cells are attracting a great deal of interest because of their simple structure and high efficiency. In these cells a free electron is excited in the organic dye and passes through a TiO2 electrode to the counter electrode. Although the structure of these solar cells is simple, a high energy conversion up to 11 % can be achieved, and the electron-transfer step resembles that in photocatalysis. Indeed, the application of dye-sensitized solar cells to the photolysis of water has also been reported, therefore a dye-sensitized TiO2 electrode should also function as a photocatalyst for the splitting of water into H2 and O2.