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

Abstract

Cs-modification effects of WO3 on photocatalytic O2 evolution and Fe (III) ion reduction over WO3 under visible light irradiation were investigated. WO3 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 WO3 was partially improved by the ion-exchange of Cs+ for H+ and Fe2+, and more than 10 times higher than that of WO3 without any treatment. The optimized WO3 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 (ηsun = 0.3%). This ηsun value is comparable to the solar-to-product energy conversion efficiencies of natural plant photosynthesis for biomass energy.