Photocatalytic behavior of cerium titanates, CeTiO4 and CeTi2O6 and their composite powders with SrTiO3

Several cerium titanates of the Ce-Ti-O system exhibit yellowish, reddish, and grayish color, because they absorb visible light (λ>410 nm). Among them, Ce2Ti2O7, Ce2/3TiO3, and Ce4Ti9O24, with mainly Ce3+, and CeTiO4 and CeTi2O6, with mainly Ce4+, were prepared and their diffuse reflectance spectra recorded, together with commercial CeTiO4(PB). The X-ray diffraction (XRD) pattern of CeTiO4 prepared by the oxidation of Ce2Ti2O7 at temperatures as low as 673 K differed from that of CeTiO4(PB). The diffuse reflectance spectra of CeTiO4, CeTi2O6, and CeTiO4(PB) indicated that the energy differences among the impurity levels in the energy band gap were relatively large; therefore, the photobleaching of methylene blue aqueous solution sensitized by CeTiO4 and CeTi2O6 powders and the respective composite powders with SrTiO3 was examined with irradiation of Xe discharge light. The composite powder of CeTiO4 with SrTiO3 was found to exert a relatively high photocatalytic activity under visible light irradiation (λ>420 nm) using a UV-cut filter