Cs-Modified WO₃ Photocatalyst Showing Efficient Solar Energy Conversion for O₂ Production and Fe (III) Ion Reduction under Visible Light

Cs-modification effects of WO 3 on photocatalytic O 2 evolution and Fe (III) ion reduction over WO 3 under visible light irradiation were investigated. WO 3 having cation-exchange ability at the surface was successfully prepared by hydrothermal and impregnation methods using cesium aqueous solutions. The photocatalytic activity of Cs-modified WO 3 was partially improved by the ion-exchange of Cs + for H + and Fe 2+, and more than 10 times higher than that of WO 3 without any treatment. The optimized WO 3 showed 48 times higher quantum efficiency (19% at 420 nm) than that reported previously under visible light, and showed a high solar-to-chemical energy conversion efficiency (η sun = 0.3%). This η sun value is comparable to the solar-to-product energy conversion efficiencies of natural plant photosynthesis for biomass energy.