Preparation And Performance Study Of Gas Diffusion Electrodes For Efficient Catalytic Electro-peroxone Process

Water pollution caused by persistent organic pollutants is a serious threat to human health and the ecological environment.Electro-peroxone water treatment technology（E-peroxone）couples electrochemical technology with ozone,where oxygen is converted to H₂O₂ by the cathode in situ electrically,which in turn strengthens ozone to produce hyperactive hydroxyl radicals（·OH）.This technology is a convenient,efficient and environmentally friendly new advanced oxidation water treatment technology with high degradation efficiency of organic matter,low energy consumption,no need for large amounts of chemical reagents,safe and no secondary pollution,and has good application prospects in water pollution control.The in situ 2e^-reduction of O₂ to H₂O₂ is considered to be the key to drive the Electro-peroxone reaction.Based on this,we promotes the efficient production of hydroxyl radicals through the modification of cathode materials to enhance the production of hydrogen peroxide.Mainly from two aspects:on the one hand,firstly,the graphite powder was modified with N and Co co-doping by mixed calcination method,followed by a simple press calcination method to successfully prepare N and Co co-doped graphite gas diffusion electrode（Co-NG GDE）with high oxygen reduction activity,and to explore the mechanism of its action in the E-peroxone process;On the other hand,considering the lack of Co-Nx active sites,the Fe,Co and N co-doped graphite gas diffusion electrode（Fe/Co-NG GDE）was prepared by introducing bimetals（Fe,Co）using the same method and applied to the E-peroxone process.In addition,we examined the effect of experimental operating conditions on the degradation of pollutants.The experimental results were as follows:（1）The Co-NG GDE prepared by a simple stepwise calcination method significantly increased the oxygen onset reduction potential（-0.05 V,150 m V higher than the unmodified graphite GDE）,increased the oxygen reduction current at the cathode and decreased the charge transfer resistance（0.4565Ω,1.9795Ωlower than the unmodified graphite GDE）.Co-NG GDE showed the highest degradation efficiency for both phenol and oxalate,but almost no H₂O₂ was generated.Characterization tests and experimental results showed that Co-NG GDE produced a large amount of O₂.^-during the oxygen reduction reaction and replaced H₂O₂ reacts with O₃ to produce super-active·OH rapidly,which was attributed to the new Co-Nx active site and higher pyridine N content.（2）Based on the content of the first part,the Fe/Co-NG GDE prepared by introducing bimetals has a correct oxygen onset reduction potential（of-0.025 V）and a lower charge transfer resistance（of 0.2766Ω）,and a higher degradation efficiency for pollutants,which is mainly related to its more abundant M-Nx（Fe-Nx and Co-Nx）active sites.Fe/Co-NG GDE in the E-peroxone process still mainly uses O₂.^-instead of H₂O₂ as the main reaction intermediate to enhance O₃ to generate·OH with higher oxidation activity to achieve efficient degradation of pollutants.The ozone concentration,the initial p H of the solution and the current density have some effects on the electrocatalytic activity.