Electrochemically assisted photocatalytic degradation of oxalic acid on particulate TiO2 film in a batch mode plate photoreactor

Electrochemically assisted photocatalytic degradation of oxalic acid was studied in a batch mode plate photoreactor composed of particulate TiO₂ film immobilized on Ti metal plate (Ti/TiO₂ electrode) and Pt wires immersed in a flowing film of aqueous solution (Pt counter electrode). The degradation rate of oxalic acid was followed as a function of the potential of the Ti/TiO₂ electrode, the oxygen concentration and the light intensity. The presence of oxalic acid caused an increase in the measured photocurrent by one order of magnitude which is due to its reaction with photogenerated holes. The degradation rate increased with increasing potential up to 0.5 V vs SCE, then the increase was more gradual. Electrochemically assisted photocatalytic degradation of oxalic acid also proceeded in the absence of oxygen. The photogenerated electrons caused hydrogen evolution (low oxygen concentration) or predominantely oxygen reduction (high oxygen concentration) on the Pt counter electrode.