Preparation of tabular TiO₂–SrTiO_3–δcomposite for photocatalytic electrode

Abstract

To improve the efficiency of photo-induced reactions, the recombination of photogenerated electrons and holes in semiconductor must be suppressed. We have proposed that the utilisation of n+/n heterogeneous junction which yields a large potential gradient in the junction region. Up to now, we have studied the superiority of such junctions in the photocatalytic reaction using composite particles consisting of TiO2 and several alkaline-earth titanates. In this study, the preparation of tabular composite consisting of TiO2 and SrTiO3–δwas examined focusing on morphologies and crystallographic features of oxides. The ideal configuration of tabular composite is the layered structure of n-type TiO2/n+-type semiconductor/metal or the mixed one partially containing such structure pass. The tabular composite was prepared by an oxidation of metallic Ti chips covered with SrCO3 powder. By such simple preparation method, the composite with designed oxides such as TiO2 and SrTiO3–δwas obtained on the Ti substrates. The grain size and the volume fraction of constituent oxides depend strongly on the oxidation temperature. When the composite is prepared at 1173 K, the grain size of oxides is measured to be about 0.5–1.0 μm. In contrast, a remarkable grain coarsening and an increase in the volume fraction of TiO2 can be observed in the oxidation at 1273 K. Furthermore, the developed texture of composite was strongly influenced by that of the Ti substrates and the oxidation temperature. Thin TiO2 layer on the surface of SrTiO3–δ phase was prepared by acid solution treatment, the designed configuration of composites could be obtained.