Preparation Of O/F Co-doped CNTs Modified Oxygen Reduction Cathode And Study On Electro-fenton Catalytic Degradation Performance Of Dye Wastewater

H₂O₂ is a very important industrial raw material and chemical reagent,and has extensive applications in medical,food and industrial fields.At present,the main industrial production method of H₂O₂ is the anthraquinone method,but it has potential hazards in transportation and storage for H₂O₂,which increase the application cost.Therefore,a method of in-situ production of H₂O₂ is needed to replace the traditional method.In this work,we use H₂SO₄/HF to acidify CNTs,prepare O or F single doped CNTs and O/F co-doped CNTs,which are used as electrocatalysts to be loaded on graphite felt for electroreduction to produce H₂O₂.Through the characterization by SEM,TEM,XRD,XPS,FT-IR and other means found that the degree of defects of CNTs increased after acidification,but the original structure of CNTs did not change.At the same time,the content of O/F functional groups of CNTs increased after acidification,especially when the ratio of H₂SO₄ to HF was 1:1（CNTs-1:1）,the ratio of COOH and CFX（X≥2）functional groups was the highest.Electrochemical testing by rotating disk electrode（RDE）found that CNTs-1:1 has the highest2-electron ORR electrocatalytic activity and selectivity.The K-L equation was used to calculate the number of electron transfer numbers of CNTs-1:1,it was close to 2 in a wide potential range,and the catalyst was still relatively stable after 10 h cycle.Then we made the CNTs before and after the modification into electrocatalytic cathode,and the single-factor H₂O₂ production experiment was carried out without aeration.The results showed that GF/CNTs-1:1 has the highest H₂O₂ yield(the concentration is 232.2 mg·L^-1 for 1h)under the best operating conditions（pH=7,constant current 0.1 A）,and has good performance at pH=1-9.It indicates that the increase in electrocatalytic activity of CNTs is mainly due to the introduction of O/F-containing functional groups,especially COOH and CF_X（X≥2）and their synergistic effects.Further,with coating of an optimized 30%PTFE film,the CNTs-1:1 exhibited extremely high activity and superior stability(the yield is 263.2 mg·L^-1 for1 h).At the same time,the stability of the cathode had been significantly improved,and it had only dropped by about 10%after 15 cycles.The composite cathode was applied to the electro-Fenton system to degrade methyl orange.The degradation performance of the Fe Mo-GICN prepared by the one-step pyrolysis method was significantly higher than that of the traditional iron catalyst(under the operating conditions with the highest H₂O₂ yield,Fe Mo-GICN was about 3 times that of Fe²⁺).The best conditions for single factor experiment determination were pH 7,Fe Mo-GICN dosage 40 mg,and initial pollutant concentration 20 mg·L^-1,and the degradation process compound first-order reaction kinetics.Inhibition experiments and EPR characterization showed that·OH was the main active substance to degrade methyl orange,and the electro-Fenton system also produced a small amount of·SO4^-.In addition,the electro-Fenton system has a good removal effect on multiple organic pollutants.This study provides a facile strategy for synthesizing a 2-electron ORR electrocatalysts with synergistic effect between hetero-atoms containing functional groups,which will provide opportunities for developing highly efficient,cost effective,and durable metal-free electrocatalysts for H₂O₂ evolution and wastewater treatment in a wide pH range.