Preparation and photoelectrochemical properties of porous thin films composed of submicron TiO2 particles

Porous thin films composed of spherical TiO2 particles of 0.6-0.7 and 0.3-0.4 mu m in diameter were prepared from Ti(OC2H5)(4) solutions containing HPC (hydroxypropylcellulose) and HNO3, 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 TiO2 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 HNO3-containing solution, probably because of the larger amount of Ti3+ species and mesopores formed in the former electrodes. The effects of post-heat-treatment on the photoanodic properties were also investigated. (C) 2000 Elsevier Science S.A. All rights reserved.