Study On The Fabrication Of Bismuth Oxychloride Based Electrode Material And Its Electrocatalytic Performance

Bismuth oxychloride（BiOCl）,as a two-dimensional layered material,has attracted much attention due to its unique layered structure,which consists of[Bi₂O₂]²⁺and double[Cl]^-that interleaves along the c-axis.A positive[Bi₂O₂]²⁺layer can generate an internal electric field,and a negative layer with Cl atoms can provide energy to facilitate electron transfer.Electro-Fenton（EF）is an effective persistent organic pollutant process.It can produce hydrogen peroxide（H₂O₂）in situ by oxygen reduction reaction（ORR）and further catalyze the formation of hydroxyl radical（·OH）which possesses strong oxidation.As a multi-purpose photocatalyst,BiOCl has been widely used in photocatalytic degradation of toxic pollutants.However,it has been proved that BiOCl as an air electrode of aluminum-air battery has excellent catalytic ability of oxygen reduction and can produce H₂O₂ by the action of electric field in the layer.BiOCl as a semiconductor has limited its application in electrocatalysis due to its low conductivity.Metal-supported electrodes immobilize the catalyst in the structural pores of the material by the use of binders or in-situ synthesis,the problem of low conductivity can be overcome.Therefore,it is of great significance to study the electrocatalytic degradation of organic pollutants by BiOCl and conductive substrate in the preparation of novel electro-fenton cathode materials.In this thesis,the composite cathode was characterized by many methods.The details of the study are as follows:（1）BiOCl was synthesized in situ on carbon felt（CF）by solvothermal method,and then BiOCl/CF composite cathode was prepared.The BiOCl/CF composite cathode was characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM）and X-ray photoelectron spectroscopy（XPS）.Its electrochemical properties were also studied by cyclic voltammetry voltammetry（CV）,linear sweep voltammetry（LSV）and electrochemical impedance spectroscopy（EIS）.The results showed that BiOCl/CF had high current density and strong current response.Through free radical quenching and electron paramagnetic resonance spectroscopy（EPR）,it was found that hydroxyl（·OH）participated in the electrocatalytic degradation of tetracycline（TC）,with an efficiency of 95%at 90 minutes.In addition,the measurement of the yield of H₂O₂ and the analysis of the valence state of elements before and after the reaction showed that BiOCl could promote the formation of H₂O₂,with an accumulation of 97mg/L at 70 minutes.And the cycle of Bi（0）/Bi（III）made H₂O₂ decompose to produce·OH,which was beneficial to the degradation of organic compounds.（2）Different concentrations of polytetrafluoroethylene（PTFE）were impregnated on the one side of carbon felt,and then BiOCl was loaded on the other side to study the TC degradation ability of the composite electrode.The reaction mechanism was studied by the determination of XPS,electrochemical analysis,the yield of H₂O₂,free radical capture and EPR.The results showed that BiOCl/CF+PTFE had higher current response value and larger peak area,which indicated that BiOCl/CF+PTFE had higher electrochemical activity.Radical trapping and EPR experiments showed that·OH played a dominant role in the degradation of TC by electro-fenton.The prepared Gas diffusion electrode（GDE）could establish a stable gas-liquid-solid three-phase interface,which could increase the production of H₂O₂ to 130mg/L by directly utilizing oxygen bubbles instead of only using dissolved oxygen.BiOCl could also decompose H₂O₂ into·OH in situ,thereby improving the degradation rate of TC,reaching 89%at 50 minutes.（3）CeO₂-BiOCl/CF+PTFE composite cathode was prepared by doping CeO₂ in BiOCl and used to degrade the simulated pollutant TC in electro-fenton system.It was found that the introduction of CeO₂ could increase the content of chemically adsorbed oxygen,thus improving the utilization rate of O₂ and driving the occurrence of two electron oxygen reduction reaction.The yield of H₂O₂ could reach 145mg/L.At the same time,the cycle of Ce⁴⁺/Ce³⁺could directly activate H₂O₂ to produce hydroxyl radical.In addition,the presence of CeO₂ established two redox cycles,Ce⁴⁺/Ce³⁺and Bi³⁺/Bi⁰.There was a synergistic effect in the generation and activation of H₂O₂,and the TC degradation efficiency could reach 88%at 30 minutes.