Abstract: The electrode of nanothin film of TiO2 was prepared by electrodeposition method on ITO surface. Electrochemical behavior of ITO/TiO2 electrode under UV illumination was investigated using the methods of cyclic voltammetry and AC impedance spectroscopy. A new oxidative peak appeared at 0.15 V when the TiO2 electrode was illuminated less than 253.7 nm lights. It belongs to a new species of photo induced Ti3＋. The complex-plane impedance plots for ITO/TiO2 electrode in a solution containing Na2SO4 at open circuit potential exhibit semicircular shapes. The apparent resistance decreased when the electrode was irradiated by UV light. It is confirmed that a new species was produced when the electrode of nanofilm TiO2 under 253.7 nm light irradiation. The open-circuit potential of an electro deposition TiO2 film electrode varied regularly with light on and off. This result shows that the TiO2 electrode has the typical characteristics of n-type semiconductors. It also indicates that photo-induced Ti3＋ is not stable in the solution.

Key words: TiO₂ electrode, UV light, Cyclic voltammetry, AC impedance spectroscopy