Photobleaching of methylene blue aqueous solution sensitized by composite powders of titanium oxide with SrTiO3, BaTiO3, and CaTiO3

We have examined photocatalytic reactions sensitized by composite particles consisting of titanium oxide, and perovskite-type titanate containing alkaline earth elements. The photocatalytic activities of perovskite-type oxides SrTiO3, BaTiO3, and CaTiO3 are fairly weaker than that of anatase-type titanium dioxide TiO2; however, in photobleaching of methylene blue under irradiation with Xe discharge light, the composite particles with TiO2 exerted photocatalytic activity several times that of TiO2 alone. Especially, the composite powder containing 30 mass% SrTiO3 exhibited the highest photocatalytic activity. The results imply the flow of photogenerated electrons and holes through the heterogeneous junctions in the composite particles. The photocatalytic activity of the composite powder was decreased when the SrTiO3 was doped with Ga and Y, presumably because of recombination of the photogenerated charges via oxygen vacancies created by the doping.