Study Of Oxygen Reduction Performance Of Iron-Carbon Aerogel Based On MIL-101 Precursor

As a type of electrochemical advanced oxidation process,the electro-Fenton technology can produce·OH?E°=2.8 V?which can degrade a variety of pollutants.It has the advantages of in-situ H₂O₂ generation and Fe²⁺regeneration on cathode.The performance of the cathode catalyst directly determines the in-situ formation of H₂O₂ and·OH and the rate of reduction and regeneration of Fe²⁺,which directly affects the efficiency of wastewater treatment.Therefore,the exploration of cathode catalyst materials with good comprehensive performance has become a hot spot in this field.Porous carbon is an electro-Fenton cathode material that has received extensive attention and research in recent years.Porous carbon prepared with a metal organic framework?MOF?as a precursor has unique properties,such as rich micropores,mesopores and even macroporous structures.This structure not only provides many electrocatalytic active sites,but also a convenient material diffusion path.Moreover,it can promote the adsorption of O₂,which is beneficial to the subsequent oxygen reduction to produce H₂O₂ reaction.In this study,N-MIL-FeC materials using MIL-101?Fe?as a precursor are prepared and characterized.Electrochemical testing methods were used to investigate the catalytic ability and electron transfer mechanism of the prepared N-MIL-FeC materials for oxygen reduction.Then the N-MIL-FeC were respectively loaded on carbon paper and carbon aerogel to decompose the simulated Rhodamine B?RhB?wastewater and simulated ammonia nitrogen??NH₄?₂SO₄?wastewater to optimize the reaction conditions and explore the reaction mechanism.?1?The MIL-101?Fe?was prepared by hydrothermal method and carbonized at a high temperature to obtain the N-MIL-FeC.It can be seen that the materials have a porous structure before and after carbonization by SEM and TEM and the nano-iron particles are embedded in the carbon material.The BET specific surface area of the N-MIL-FeC prepared under the optimal conditions is 515.1 m²·g^-1,and the pore diameter is mainly distributed at 0-5.0 nm.The results of XRD and XPS indicate that FeO,Fe₃O₄ and Fe⁰ are present in the material,of which Fe⁰ is the main substance.?2?Electrochemical performance tests of N-MIL-FeC show that the materials can catalyze the two-electron reduction of oxygen.The pH value of the electrolyte solution has a great influence on the reaction process,and the reaction effect is best when it is close to neutral.Carbon aerogels have an auxiliary effect on the catalytic oxygen reduction of N-MIL-FeC.The RDE results indicate that the reaction process is mainly two-electron reduction and the RRDE curve indicates that its catalytic oxygen reduction reaction can produce H₂O₂.?3?The N-MIL-FeC/C electrode was used as a cathode to degrade RhB by the electro-Fenton reaction.Under the optimal reaction conditions(catalyst loading is 1.5mg·cm^-2,pH is neutral),the degradation rate of RhB(10 mg·L^-1)is over 99.0%in 50 min.Moreover,the degradation rate of the·OH inhibitor was significantly reduced after the addition of ethanol to the reaction system,indicating that·OH is the main active substance for RhB degradation.?4?The N-MIL-FeC/CA electrode is capable of producing H₂O₂,and the accumulation amount of 4 h can reach 8.9 mmol·L^-1.In the experiment of degrading simulated ammonia nitrogen in electro-Fenton system,under the optimal conditions(N-MIL-FeC loading is 1.5mg·cm^-2,current is 75 mA,initial solution pH is 7,aeration is 0.7 L·min^-1,reaction temperature is 25?),the initial concentration of 40 mg·L^-1 ammonia nitrogen degradation rate of 96.8%.Both the free radical quenching experiment and the EPR test detected the presence of·OH,which proved that·OH is the main active intermediate in the degradation process.