Abstract: A three-electrode system composed of TiO₂ photoelectrode as the working electrode,Pt ring as the counter electrode and saturated calomel electrode (SCE) as the reference electrode was used for the photoelectrocatalytic degradation of phenol.The TiO₂ thin film photoelectrode was made by anodizing.During the photoelectrocatalytic process,Electrochemical Impedance Spectroscopy (EIS) was applied to measure the capacitance of space charge layer in the TiO₂ semiconductor photoelectrode,and to calculate the band structure parameter-the width W of space charge layer.The results show that photocatalytic activity of TiO₂ electrode is improved when the width broadens with the bias increasing; the activity reaches best when the width is nearly equivalent to the thickness of TiO₂ thin film,then the optimal value of the bias appears; the activity somewhat decreases when the bias is beyond the optimal value.

Key words: TiO₂ thin film, semiconductor photoelectrode, electrochemical impedance spectroscopy, phenol degradation