Effect of applied potential on photocatalytic phenol degradation using nanocrystalline TiO2 electrodes

The activity of transparent and highly porous nanocrystalline TiO2 electrodes for phenol degradation by heterogeneous photocatalysis was investigated. Electrochemical characterization, performed for electrodes with areas = 1.0 cm2, revealed that the capacitance values increased under irradiation. Electrodes with areas = 9.0 cm2 were used for remediation of 10 mL of an aqueous solution containing 50 mg L−1 of phenol. Irradiated by a solar simulator, removal of 48% of total organic carbon was achieved after 3 h. The efficiency was significantly enhanced for electrochemically assisted photocatalysis; the average mineralization was 78% after 3 h and was almost complete after 6 h for a TiO2 electrode externally connected to a Pt counter-electrode and biased at +0.7 or +1.1 V with a potentiostat, or by a series connection to a solar cell. Phenol degradation exhibited pseudo-first-order kinetics, and application of the bias potential increased the rate constant from 0.21 to 0.47 h−1. Applying a potential bias to the TiO2 electrode minimizes the recombination of photogenerated charge carriers and enhances the photocatalytic activity towards organic pollutant degradation.