Photoelectrochemical characterisation of thermal and particulate titanium dioxide electrodes

The photoelectrocatalytic performance of thermal and particulate TiO2 films on Ti electrode substrates has been studied by photovoltammetry and bulk photoelectrolysis. The thermal TiO2 film electrodes were prepared by Ti annealing in air at 700 °C and 500 °C while the particulate electrodes were prepared from dispersions of Degussa P-25 TiO2 deposited onto Ti substrates and subsequently sintered at 700 °C and 500 °C. The photocurrent in the absence and presence of the model organic species of oxalate as well as its photooxidation rate depends on coating surface area, type (thermal or particulate) and crystallographic form (anatase or rutile). A method is proposed to account for surface area variations by normalising the data with respect to the electroactive surface area of the TiO2 electrodes, as estimated by their surface electrochemistry in the dark. The thermal electrodes show high photocurrents both in the absence and the presence of oxalate whereas the performance of particulate electrodes is significantly improved upon oxalate addition. Nevertheless, the efficiency of thermal 700 °C TiO2 for oxalate photooxidation during bulk photoelectrolysis is comparable to that of Degussa P-25 TiO2-coated electrodes.