Water Splitting into H2 and O2 over ALa4Ti4O15 (A=Ca, Sr, and Ba) Photocatalysts with Layered Perovskite Structure

  • Mr Yugo Miseki, Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, Japan
  • Dr Hideki Kato, Materials and Structures Labratory, Tokyo Institute of Technology, Japan
  • Akihiko Kudo, Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, Japan

    • Development of active photocatalysts for water splitting into H2 and O2 is an important topic. In the present study, photophysical and photocatalytic properties of ALa4Ti4O15 (A=Ca, Sr, and Ba) with layered perovskite structure were investigated. ALa4Ti4O15 (A=Ca, Sr, and Ba) powder was prepared by a polymerizable complex method. Water splitting reactions were carried out in a gas-closed circulation system equipped. In an inner irradiation reaction cell made of quartz equipped with a 400-W high-pressure mercury lamp. The amounts of evolved H2 and O2 were determined using on-line gas chromatography. Diffuse reflection spectra indicated that the band gaps of ALa4Ti4O15 (A=Ca, Sr, and Ba) were 3.8~3.9eV. Native BaLa4Ti4O15 showed no activity for water splitting. In contrast, NiO/BaLa4Ti4O15 showed high activity for water splitting when the pretreatment of H2 reduction at subsequent O2 oxidation was carried out. The activity of NiO/BaLa4Ti4O15 was higher than that of NiO/CaLa4Ti4O15. This is due to difference in distribution alkaline earth cations and La between CaLa4Ti4O15 and BaLa4Ti4O15 at perovskite slab and interlayer space. The optimized NiO (0.5 wt %)/BaLa4Ti4O15 photocatalyst steadily produced H2 and O2 at the rates of 2.4 and 1.2 mmol/h, respectively. The apparent quantum yield was 15% at 270 nm. In conclusion, ALa4Ti4O15 (A=Ca, Sr, and Ba) with layered perovskite structure was found to be new photocatalyst materials for water splitting.