The Construction Of Modified Graphite Felts Porous Self-standing Carbon Materials And Their Electro-Fenton Performance

As an advanced oxidation technology with good controllability,high efficiency and cleanliness,the electro-Fenton（EF）technology has drawn more and more attention and research in the field of water treatment.However,drawbacks such as poor performance and slow degradation kinetics caused by poor catalytic activity,bad hydrophilicity and small specific surface area of the raw graphite felt（RGF）limit its practical application in the electro-Fenton process.In particular,the small specific surface area of graphite felt fibers is not conducive to the exposure of oxygen-reducing active sites and the rapid mass transfer for three-phase reactions,all of these block graphite felts as cheap self-standing carbon materials to directly serve as electro-Fenton cathodes.Therefore,it is necessary to design and prepare a highly active graphite felt cathode with rich pore structure and remarkable hydrophilicity to obtain higher performance and efficiency of electro-Fenton.In this paper,two different etchants are used to construct the rich pore structure on the surface of graphite felt fibers and as modification method to improve hydrophilicity.The modified graphite felts with large specific surface area,high Fenton activity and good durability are obtained as cathode materials.A holey graphite felt（HGF）electrode with rich porous structure was prepared by a method combining static growth of metal organic frameworks（MOFs）and thermal reduction.The MOFs derivation method was gentle and efficient,and nano-scale pore channels were evenly distributed on the surface of graphite felt fibers.The rich three-dimensional structure and excellent hydrophilicity of HGF leads to outstanding degradation kinetics in degrading rhodamine B（RhB）dyes by electro-Fenton process,and the dyes can be completely decolored in 3 minutes.The removal efficiency of ciprofloxacin and p-nitrophenol is also excellent.The improvement of degradation rate is about 80.6%and 20%,and the removal of total organic carbon is increased by 45.6%and 20.7%compared with the RGF,respectively.The superior hydrophilicity of HGF is conducive to the transfer of reactive substances in the electrolyte and the interaction with the electrode surface.In the meanwhile,it accelerates the rapid conversion of reactive substances.FeOOH,as a low-toxic and low-cost etchtant,is used to modify the RGF.FeOOH nanorods were uniformly grown on the surface of graphite felt fibers by a simple hydrothermal method.After the thermal treatment,Fe₃O₄ modified graphite felt electrodes（Fe₃O₄@GF）were obtained.Fe₃O₄ nanoparticles can directly act as the catalyst in the first round electro-Fenton reaction,which further simplifies the processes and reduces the cost of experiments.The Fe₃O₄@GF electrode is used for the degradation of RhB dyes with outstading degradation activity.RhB can be completely decolored in 5 minutes,and compared with RGF,the fresh Fe₃O₄@GF exhibits superior pollutant degradation kinetics with more than 400%increase and approximately 37.8%improvement to the removal of total organic carbon.Following with the participation of Fe₃O₄ nanoparticles in the Fenton reaction,porous graphite felts（PGF）with rich pore structure was obtained.PGF shows pretty good performance of H₂O₂ production.Further researches on the strengthening mechanism of electro-Fenton and hydrogen peroxide production are carried,it is inferred that the increased specific surface area,rich defects and sp³-C can serve as active sites for oxygen reduction.The degradation performance of PGF does not significantly decay even after 20 times repeated use,indicating the good structural stability and long-term durability.This holey-engineered strategy by Fe based oxides also provides the possibility to achieve swift water purification and open up a new way for developing efficient carbon-based electrodes.