Two Photoelectrochemical Processes for TiO2 Electrode under UV Illumination

TiO 2 thin film electrode was prepared by a sol gel method on ITO substrates. Cyclic voltammetric behavior of the ITO/TiO 2 electrode under ultraviolet (UV) illumination was investigated in the solution of Na 2SO 4. There are two photoelectrochemical processes for TiO 2 electrode under UV illumination. One is a fast process, which results in the appearance of anodic photocurrent. The anodic photocurrent will appear and disappear with the light on and off. The other is a slow process, which will be responsible for the appearance of an oxidative peak. When the electrode is illuminated under UV light for a long time, a new oxidative peak can be observed. The peak current increases with the increase of UV illumination time. It is assumed that the new peak belongs to the oxidation of Ti 3+ , which formed and accumulated on the electrode surface during the UV illumination. A detailed mechanism is proposed on the base of these two photoelectrochemical processes. It is assumed that the change of hydrophilicity of TiO 2 thin film may be related to the slow process while the film irradiated by UV light.