Impedance Analysis Of Mn And Ce Doped TiO₂ Catalysts And Study On Photocatalytic Degradation Methyl Orange

Recently,water pollutants were increasing quantitatively and qualitatively.Among the various pollutants,organic pollutants have attracted attention due to their complexity and non-biodegradability.TiO₂ photocatalytic technology can produce hydroxyl radicals?OH·?with strong oxidative activity by light to degrade complex organic pollutants.Various study had been done to enhance the photoelectric efficiency,increase the recombination time of the electron-hole,and improve the catalytic ability of the catalysts.At present,the research of this field was mainly to study the impedance spectra of single doped TiO₂ catalysts.In this paper,the impedance spectra of Mn and Ce co-doped photocatalysts have been studied for the first time,which was important for understanding the electron transfer and interfacial particle transfer process of this catalysts.In this paper,the working electrode of Ce and Mn-doped TiO₂ catalyst was prepared by sol-gel and dip-coating method.The electrolytic cell system was constructed with the platinum electrode as the counter electrode and the saturated calomel electrode as the reference electrode.XRD,SEM,EDS and UV-vis were used to characterize the surface catalyst and microstructure of the electrode,revealing that Mn doping effectively reduced the dispersion of the catalysts,and Ce doping introduced Ce?III?and Ce?IV?oxide into the catalyst.After doping,the forbidden-band width of Ce/TiO₂,Mn/TiO₂ and Mn-Ce/TiO₂ were reduced by 0.26 eV,1.17 eV,1.94 eV,respectively.In the K₂SO₄ electrolyte,a three-electrode system was used to plot the impedance spectrum.By the comparative study of four catalysts electrode on dark state and UV irradiation with different bias voltage,it was found that the application of bias voltage and UV light can obviously reduce the reaction process impedance,improve the catalyst film catalytic performance.When the bias voltage was around-0.7V,the reaction impedance was the lowest.Then,equivalent electrical circuits fitting was used to analyze the EIS by analysis software Zsimpwin.The model I,IV,V and IV were chosen as the fitting model of TiO₂,Ce/TiO₂,Mn/TiO₂ and Mn-Ce/TiO₂ respectively by analysing the catalysts thin film physical properties,degradation process performance and impedance spectroscopy.The fitting results show that the increase of conductivity after Ce doped show up as decrease of R_SC,the improvement of photoelectric effect and the degradation performance after Mn doped correspond to the increase of C_SC and CPE.The increase of C_SC and the decrease of R_SC were obvious on UV irradiation.The voltage bias had the effect of reducing the impedance of each electronic component.Finally,four kinds of catalysts were used as working electrode for photocatalytic degradation of methyl orange,the three-electrode system was used as the impedance detection and reaction system.After the study under different conditions of catalysts,bias voltage,irritation conditions,it was found that the best degradation method was the photoelectrocatalytic degradation by Mn-Ce/TiO₂ thin film electrode and the best bias was-1.0V.In this paper,the method of characterizing the photoelectrocatalytic activity of Mn and Ce doped TiO₂ catalyst system by EIS was established,the electrochemical properties of the catalyst were correlated with the fitting of electronic components parameters.In this paper,the photoelectrocatalytic activity of Mn and Ce doped TiO₂ catalysts was characterized by impedance spectroscopy?EIS?in the dark and under UV irradiation,respectively.The photocatalytic performance of the catalyst was correlated with the equivalent circuit model parameters by the analysis of equivalent circuit fitting.