Study On Preparation And Performance Of Titanium Dioxide Composite Electrodes Assisted By Dielectric Barrier Discharge

Photoelectrocatalytic technology,has been used in wastewater treatment widely due to high treatment efficiency and no secondary pollution causing.The key to the technology is the research and development of photocatalyst.At the same time,material modification and material preparation by dielectric barrier discharge（DBD）plasma technology could increase the introduction of surface-active species on the materials,which promote the improvement of photoelectrocatalytic performance of materials.In this paper,the titanium dioxide nanorods prepared by hydrothermal method was used as substrate,modified and prepared by dielectric barrier discharge plasma with a view to improving the efficiency of the electrodes for pollutant treatment.And the mechanism for degradation of pollutant was also discussed.Firstly,the g-C₃N₄ and Ag₂O powders were modified by DBD.The g-C₃N₄/Ag₂O/TiO₂nanorods electrodes were synthesized by two-step deposition method.The result showed that ternary electrodes prepared by g-C₃N₄ and Ag₂O with 5 min for modification possessed best activities by changing the plasma discharge time（0,5,10,20 min）.And the difference of the ternary composite electrode obtained by the optimal plasma treatment conditions,and without plasma treatment was characterized by XPS and XRD analysis.The results showed that a large amount of oxygen-containing active substances were induced during the plasma treatment,which play a role in surface of materials and change the surface valence state of the material.Thus,the photoelectrocatalytic performance of the ternary composite electrode was improved.The phenol aqueous solution was used as the treatment target,and the g-C₃N₄/Ag₂O/TiO₂-NRs electrode was used as the working electrode,with establishment of electrophotocatalytic reaction system,under the conditions of pH=3 and pH=5.85,the effects of different catalytic methods,different composite electrodes and external bias voltage on the treatment of pollutants were studied.The degradation reaction showed that the removal efficiency of phenol was the at the plasma discharge time of 5 min for modification of two powders further.The degradation of phenol was approximately 73.27%at pH=3 and 58.54%at pH=5.85 within 2 h on PEC,respectively.Under acidic conditions,the removal efficiency of phenol was increased due to the increase of hydroxyl radicals,which play a role in the photocatalytic reaction.Considering the energy consumption problem,it is determined that in the photoelectric catalytic mode of 3 V and pH=3 were the optimal conditions.The electronic transfer of the system was studied by the addition of Cr（VI）.The results show that in this reaction system,the addition of Cr（VI）does not improve the electron transfer to the cathode.The study of active species showed that the main active species are O₂?^-and?OH.The possible mechanism of photoelectrocatalytic degradation of phenol for g-C₃N₄/Ag₂O/TiO₂-NRs electrodes was studied based on above results.We prepared g-C₃N₄/Mn₃O₄/TiO₂-NRs electrodes by using an earth-abundant Mn₃O₄instead of precious metal oxide Ag₂O.SEM and XPS showed that Mn₃O₄ was successfully loaded on TiO₂ nanorods.Photocurrent analysis showed that plasma modification has no significant improvement of photoelectrocatalytic performance for Mn₃O₄.Taking phenol as the target pollutant,the influence of different catalytic methods,composite electrodes,applied bias voltage,initial pH,initial concentration of pollutants on the photoelectric efficiency were studied.The results showed that,the degradation rate of phenol with an initial concentration of 10 mg/L was 70.41%within 2 h in PEC system when the bias voltage was 3 V and pH unadjusted at g-C₃N₄-5/Mn₃O₄/TiO₂-NRs electrodes,which was prepared by g-C₃N₄ modified for 5 min and Mn₃O₄ unmodified.On this basis,we focused on the one-step deposition by plasma treatment,and CeO₂/TiO₂-NRs electrodes was synthesized.XRD and TEM analysis showed that composite material mainly exists in the form of CeO₂（111）crystal plane.Various processing voltage and time has a great effect on the photocatalytic performance of the electrode material.The composite electrode has the best photoelectric performance with discharge voltage at 45 V and the treatment time at 10 min of which photocurrent density was about 5 times higher than that of single titanium dioxide nanorods under UV-visible light irradiation when the bias voltage was 0.6 V.Taking phenol as the target pollutant,the degradation efficiency of CeO₂/TiO₂-NRs electrodes was investigated.In PEC system,the degradation rate of phenol with an initial concentration of 10 mg/L was 70.41%at CeO₂/TiO₂-NRs electrodes within 2 h when the bias voltage was 3 V and pH unadjusted.The results of cyclic experiments showed that the CeO₂/TiO₂-NRs electrodes have good stability.Through the modification and preparation of three materials,we found that plasma technology can promote the photoelectrocatalytic performance of materials,which can be attributed to a large amount of oxygen-containing active materials induced on the surface of the material during the discharge processing.At the same time,preparation of composite electrode materials by plasma treatment has shorten the electrode preparation process effectively.In this paper,the prepared three electrode materials show stable and efficient degradation performance,which provid a certain theoretical basis for the research of DBD technology in the field of environment and materials.