Preparation of platinized strontium titanate covered with hollow silica and its activity for overall water splitting in a novel phase-boundary photocatalytic system

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 (H2) and oxygen (O2). Probably due to the suppression of a backward reaction, production of water from H2 and O2, 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.