Platinum-loaded strontium titanate (Pt-SrTiO3) (core) -silica (shell) powder was prepared by double-layer winding of a carbon and a silica layer on Pt-SrTiO3 followed by heat treatment to remove the carbon layer. Scanning electron microscope (SEM) observation and analyses of the BET surface area suggested that the powder has a void space between Pt-SrTiO3 (core) and silica (shell). When the surface of the powder was partially modified with a fluoroalkylsilylation agent, thus-obtained material assembled at a gas-water interface and acted as a photocatalyst for overall water splitting to produce hydrogen (H-2) and oxygen (O-2). Probably due to the suppression of a backward reaction, production of water from H-2 and O-2, on the platinum, the overall efficiency of this system was higher than that of the conventional suspension system. Moreover, while the Pt-SrTiO3 powders directly covered with fluoroalkylethylsilyl groups showed low photostability, i.e., prolonged irradiation precipitated some of the surface-modified particles in water owing to photocatalytic decomposition of surface fluoroalkylethylsilyl groups, this material could retain its location at the phase boundary. (C) 2006 Elsevier B.V. All rights reserved.