Study On The Properties Of TiO₂ Photocatalyst By AC Impedance Method

In this paper, Nano-TiO₂ thin film was prepared on the surface of porous Al2O3 film by the sol-gel processing and dip-ping-plugging method, The microstructure and the surface physical property of film were measured by using SEM, UV-Vis technology and XRD.1.Under the black light,The film was used in the degradation of methyl orange. And then the AC impedance spectra of the TiO₂ semiconductor-photocatalyst in the system was detected and analyzed by a Frequency Spores Detector (TD1250) with its relevant powersine software 3691dms under conditions of having no lights,light with various wavelengths and changed anodic bias. At the same time, compared the AC impedance spectra of the TiO₂ thin film by two different preparation method. From the point of view about the change of the AC impedance in the system, We discussed illumination and the anodic bias on the photocatalyst in the process of methyl orange on the aspect of impedance. The results of the following experiments of methyl orange degradation were identical to the former conclusions.The result indicated that the AC Impedance spectra can reflected the experiment process of the photocatalysis and the electrolphotocatalysis preferably; Besides additiong of anode voltage could improved the catalyse performance of the film, and the effect quite well over 0.4V;2.The AC Impedance data were dealt with analytic Software ZsimpWin of Equivalent Circuit. Combined with the characteristics of semiconductor photo-electrode, Three kinds of equivalent circuit models of TiO₂ semiconductor-electrode system were put forward, which Model I CDC code is R(RC)(RQ) and Modelâ…¡is R(R(CQ)), and Modelâ…¢is R(Q(R(RC))) respectively . Here compared with plenty of simulated results of different experiments, the Modelâ…¢was determined to be the best rational one.3.The characteristic of semiconductor/solution was analyzed in system. Then component value of equivalent circuit in the methyl orange system was applied to calculate the energy band structure parameter of TiO₂. Moreover, the connection between the photocatalyst of TiO₂ semiconductor and the energy band of the semiconductor was analyzed. At the same time, the space charge layer width W the major factor which determine the TiO₂ photocatalysis in the energy band structure parameter. The energy band structure parameter of TiO₂ and the AC impedance spectra was contacted, accordingly understand the photocatalysis of TiO₂ from the theory.The energy band structure paramete can calculated from the data of the AC Impedance spectra, the vacuum charge floor width was an important parameter of catalyse performance, anode voltage made it came broden, when the width was equal to the film thickness, the catalyse activity was quite well.In this paper,a method of AC impedance to characterize the activity of TiO₂ semiconductor photoelectrode in the condition of reaction with different applied bias is preliminarily put forward.