Study On Relation Between Band Structure Of Thin TiO₂ Photoelectrode And Catalytic Activity With Electrochemistry Impedance Spectroscopy

In this paper, Electrochemistry Impedance Spectroscopy (EIS ) is used to study the heterogeneous photocatalystic system of TiO2 semiconductor in the condition of reaction.The EIS of the thin Ti02 photoelectrode in Phenol system was measured and analyzed by a Potentiostat(M273A) and a Frequency Spores Detector (Ml 025) with its relevant PowerSuite software under conditions with light or without light, and with changing applied bias. Also, the influence of light and bias on the photoelectrocatalytic process was discussed with the EIS change. The results of the following experiments of phenol degradation were identical to the former conclusions.The EIS data was dealt with analytic Softward ZsimpWin of Equivalent Circuit. Three kinds of equivalent circuit models of thin TiO2 photoelectrode system were put forward, the circuit describing codes (CDC) as follows: the Model I is R(RC)(RQ), Model II is R(R(CQ)), and Model III is R(C(R(RQ))) respectively. Here compared with plenty of simulated results of different experiments, the Model IIIwas determined to be the better one. In addition, using the values of the equivalent circuit parameters in Phenol system, the energy-band structure parameter, the width W of space charge layer, was calculated. The results show that photocatalytic activity of TiO2 electrode is improved when the width broadens with the bias increasing, the rate of phenol degradation is faster; the activity reaches the best when the width is nearly equivalent to the thickness of thin TiO2 film, the rate is the fastest, then the optimal value of the bias appears; the activity somewhat decreases when the bias is beyond the optimal value, the rate becomes slower.EIS is also used to study the inorganic FeSO4 system, with coated TiO2 photoelectrode; the traditional CV technique is further applied to study the activity of TiO2 photocatalyst in this system. The results of the system are proved that the method of EIS is reasonable to characterize the activity of semiconductor photoelectrode.In this paper, a new method of EIS to characterize the activity of TiO2 semiconductor photoelectrode in the condition of reaction with different applied bias is preliminarily put forward.