Photocatalytic activity enhancement of TiO2 thin films with silver doping under visible light

TiO2 and silver doped TiO2 films (photoanodes) were prepared by the sol–gel method using silver contents of 1%, 3% and 5% (w/w). Photoelectrocatalytic activity of these photoanodes was evaluated by monitoring the photocatalytic decomposition of methanol and basic orange II (BOII) in aqueous solution under visible light illumination at pH 3 adjusted with HClO4 by the application of potential bias. Enhanced photoelectrocatalytic activity was found by the application of 0.4 V (vs. SCE) bias potential under visible light illumination. A detrimental effect was observed on the photoelectrocatalytic activity of the TiO2 photoanodes in the presence of BOII, and is evident from the low photocurrents; however, the presence of silver in the TiO2 films increased the photoelectrocatalytic activity. Also the photoelectrolysis of methanol removed over 80% of total organic carbon in 5 h of reaction under visible light and 0.4 V (vs. SCE) bias potential. Nevertheless, negligible TOC removal was observed for the BOII photoelectrolysis with or without bias potential and under visible light illumination or in dark. Less than 9% of discoloration was achieved at the 3% Ag–TiO2 photoanode under visible light illumination and bias potential.