Fabrication of SrTiO₃ exposing characteristic facets using molten salt flux and improvement of photocatalytic activity for water splitting

Flux treatment using various molten salts was performed for SrTiO ₃ powders. Morphology of SrTiO₃ crystals obtained by the flux treatment strongly depended on the kinds of molten salts used. Large cubic crystals exposing {100} facets with a size of 5-6 μm were obtained by the flux treatment with LiCl whereas truncated cubes exposing {100} and {110} facets with a size of 200-400 nm were obtained when NaCl or SrCl₂ was used as a flux reagent. In contrast, the flux treatment with KCl gave characteristic shaped crystals with a size of 300 nm. Electron microscope observation and electron diffraction analysis revealed that the crystals treated with the KCl flux expose {100}, {120}, and {121} facets. SrTiO₃ treated with the KCl flux exhibited higher activity by 20 times than the non-flux-treated sample. Thus, a remarkable improvement of activity has been achieved by the fabrication of SrTiO₃ crystals exposing high-index facets, {120} and {121}, using the KCl flux.