Photocatalytic behavior of titanium oxide-perovskite type Sr(Zr1−xYx)O3−δ composite particles

Photocatalytic reactions sensitized by composite particles have been examined, which are composed of titanium dioxide and acceptor-doped perovskite involving alkali-earth elements. Although the photocatalytic activity of perovskite-type oxide Sr(Zr0.90Y0.10)O3−δ being p-type conductor is weak, it absorbs light with wavelength of λ<800 nm. Titanium dioxide (TiO2) being n-type conductor exhibits a fairly high photocatalytic activity; however, it does not absorb visible light. Under the irradiation of Xe discharge light, the composite particles involving the pn-junction exerted several times higher photocatalytic activity in photodegradation of methylene blue than a sole TiO2. Similar results were obtained for the composite powders of Sr(Zr0.95Y0.05)O3−δ, Ca(Zr0.95Y0.10)O3−δ and Ca(Zr0.95Ga0.05)O3−δ with TiO2, respectively. Under the irradiation of visible light with wavelength of λ>420 nm, it was found that the photodegradation of methylene blue and HCOOH aqueous solutions proceeded. These results may be explained by a model for the flow of the photogenerated electrons and holes through the pn-junctions in the composite particles.