Photoelectrocatalytic degradation of potential water pollutants in the presence of NaCl using nanocrystalline titania films

BACKGROUND Photocatalytic degradation using nanoparticulate titania films does not provide sufficiently high specific surface area for fast pollutant degradation. This deficiency can be corrected by electrocatalytic and photoelectrocatalytic processes. RESULTS Nanocrystalline titania films have been deposited on transparent conductive electrodes and were used for photocatalytic and photoelectrocatalytic discoloration of the anionic Acid Orange 7 and the cationic Rhodamine 6G under simulated solar radiation. Experiments have been conducted in the presence of either NaCl , as a natural active species, or Na 2 SO 4 , as a relatively inert electrolyte. Photocatalytic discoloration was relatively slow but the process was highly accelerated by applying an electric bias, both in the forward and the reverse direction, particularly in the presence of NaCl . Application of forward bias assisted photogenerated electron–hole separation and affected attraction or repulsion of the charged dyes towards the photocatalyst. However, both effects were masked by the strong electrocatalytic effect produced in the presence of NaCl when Cl‐based oxidative species could be created on either of the two electrodes under any electric bias. As expected, such electrocatalytic effects were much slower in the presence of SO 4 2 ‐ instead of the highly active Cl ‐ anions. CONCLUSIONS Degradation of model pollutants can be accelerated in a photoelectrochemical cell using the same quantity of photocatalyst. The natural electrolyte NaCl additionally allows for strong electrocatalytic effects, which were obtained at moderate applied electric bias. © 2014 Society of Chemical Industry