Photo-chargeable titanium/vanadium oxide composites

Titanium and vanadium oxides were prepared by a sol–gel technique and supercritical drying and evaluated for light energy conversion and storage in a wet-type photoelectrochemical cell. Ultraviolet light irradiation to the nanocrystalline titania aerogel (anatase) produced significant photocurrents, and the maximum incident photon-to-current conversion efficiency (IPCE) attained 37.1%. From cyclic voltammetry, the vanadium oxide gel was shown capacitive for charge storage, associated with the shcherbinaite structure and V4+/V5+ redox pair. Photopotential responses revealed that coupled TiO2/V2O5 composites not only were photo-chargeable but also exhibited a greater discharging capacity than the TiO2 or V2O5 alone. The discharging capacity was remarkably reduced in the presence of dissolved oxygen. Results demonstrate that in the hybrid TiO2/V2O5 system the V2O5 serves to accumulate photoelectrons generated by the illuminated TiO2 during the photo-charging process. A schematic energy diagram that describes the band structure of the composite semiconductor is proposed.