Preparation and photoelectrochemical properties of porous thin films composed of submicron TiO 2 particles

Abstract

Porous thin films composed of spherical TiO 2 particles of 0.6–0.7 and 0.3–0.4 μm in diameter were prepared from Ti(OC 2H 5) 4 solutions containing HPC (hydroxypropylcellulose) and HNO 3, respectively, and the photoelectrochemical properties as a photoanode were investigated in a wet cell. The electrode samples showed higher anodic photocurrent and higher UV photoresponse than relatively dense TiO 2 thin film electrodes prepared by dip-coating, and exhibited weak but distinct visible light photoresponse. These experimental results show that the submicron colloidal electrodes have high specific surface area effective for the photo-induced redox reactions. It also suggests the formation of the band bending that contributes to the photocurrent generation. The colloidal electrodes prepared from the HPC-containing solution were found to exhibit higher anodic photocurrent than those from the HNO 3-containing solution, probably because of the larger amount of Ti 3+ species and mesopores formed in the former electrodes. The effects of post-heat-treatment on the photoanodic properties were also investigated.