Photoelectrocatalytic study and scaling up of titanium dioxide electrodes for wastewater treatment.

Different TiO2 photoelectrodes have been characterized and tested for the photoelectrocatalytic oxidation of methanol. Particulate electrodes (TiO2/Ti and TiO2/ITO) have been shown to notably favour charge-carrier transfer at the electrolyte interface while a thermal electrode (Ti) has been shown to favour charge-carrier separation when applying an electric potential bias according to cyclic voltammetry technique, as a consequence of differences in TiO2 surface between particulate and thermal electrodes. Particulate electrodes lead to a higher photoelectrocatalytic activity for methanol oxidation compared to that of the thermal electrode, probably due to the pure-rutile TiO2 phase composition of the latter and its lower surface area. TiO2/Ti electrode has been shown to be the most effective photoelectrode tested for methanol oxidation since its activity was improved by the combination of the particulate TiO2 layer and the high electrical conductivity of the support. Generally, photocurrent density measured in the photoelectrochemical cell seems to correlate with activity, whereas this correlation is not observed when using a larger photoelectrocatalytic reactor. In contrast, the activity obtained for the scaled-up electrode is found to be similar in terms of surface kinetic constant to that obtained at laboratory scale.