Application Of High Conductive Anode Materials Modified By Carbon Nitride And Graphene In Microbial Fuel Cells

Energy and the environment are indispensable and important components in our production and life,and are also the driving force for maintaining sustainable development.Although fossil energy production is highly efficient,some greenhouse gases will be generated during the use process,and at the same time,mining and consumption without a bottom line are gradually depleting it.Microbial fuel cell(MFC)can generate electricity while decomposing organic matter in water.It is a very promising new technology of clean energy from waste resources.MFC has been researched and developed for more than 20 years.Due to its low power production efficiency,high manufacturing cost,and many influencing factors,it has not been put into large-scale applications so far.Among them,the anode of MFC is a place where microorganisms grow and multiply,and it is also a place where protons and electrons are transferred.It has a greater impact on the electricity generation performance and cost of MFC.This article will focus on the study of the impact of highly conductive materials and their modified anodes on the electricity generation performance of MFC.Carbon brushes are often widely used as an anode with excellent performance.Polyacrylonitrile-based carbon fibers with poor conductivity are usually used.In this topic,mesophase pitch-based carbon fibers(MPCF)with better conductivity are used to prepare carbon brush anodes for MFC.Because the surface of untreated MPCF is relatively inert and smooth,the adhesion of microorganisms is poor.In this article,we used carbon nitride and graphene to modify the surface of carbon brushes to improve anode biocompatibility.The results show that the performance of MFC with carbon nitride modified carbon brush anode is the best,and the maximum power density can reach 800.8 mW/m2.Characterization by SEM,BET,XPS,etc.shows that g-C3N4 modification can improve the biocompatibility of the carbon fiber surface,increase the surface roughness of the material,and increase the specific surface area of the material.The surface of the material has more N-containing functional groups,and pyridine-N It can improve the surface alkalinity of the anode material and the adhesion of microorganisms.Graphite-N can promote the reduction of internal resistance and attract more microorganisms to adhere to improve the power generation performance of MFC.However,the performance of the MFC after doping with graphene has declined.It may be due to the biotoxicity of graphene.The sharp edges pierce the microbial cell membrane and cause the death of bacteria,and the biocompatibility deteriorates,resulting in poor battery performance.Due to the tight and orderly arrangement of carbon fibers in the carbon brushes,the electronic transmission lines of the carbon brush anodes are smooth and efficient.However,the carbon fibers near the center of the carbon brushes are clustered together with more than half the diameter of the carbon fibers.The effective working area is reduced and the utilization rate is low.Coupled with the high cost of carbon fiber and the difficulty of scaling up the MFC of carbon brush anode configuration,the development of a cheap and highly conductive 3D configuration anode material is of great significance to the development of MFC.This topic uses 3D configuration nickel foam and modified materials of nickel foam and graphitized mesophase pitch-based carbon foam as the anode of MFC.The 3D anode structure is uniform,has a large specific surface area,and the effective working area of the material is greatly improved.Graphitized mesophase pitch-based carbon foam has strong corrosion resistance,but the surface is smooth;foamed nickel has high electrical conductivity,but it is easy to corrode in water.Compared with carbon anodes,the cost of foamed nickel is low,which helps to greatly reduce the manufacturing cost of MFCs.Therefore,the development of foamed nickel anodes is of great significance to the promotion and application of MFCs.In this paper,the surface of the foamed nickel was modified with graphene to improve the corrosion resistance,and the electricity generation performance was studied as an MFC anode.The main results obtained are as follows:There are four types of 3D in foam nickel anode(NF),graphene hydrogel modified foam nickel anode(rGO-NF),carbon foam anode(rGO-CF)and carbon nitride modified foam nickel anode(CN-NF)Among the materials,rGONF has the most excellent electrochemical performance,achieving a maximum power density of 909.3 mW/m2,which is 1.6 times that of the NF electrode.In order to further improve the corrosion resistance of the foamed nickel electrode,this study used graphene anti-corrosion conductive coating to treat the surface of the foamed nickel and carbonized it at 700℃,1000℃,and 1300℃ to compare battery performance.The MFC treated with a high temperature of 1000℃ has a stable output voltage of 550 mV and a maximum power density of 747.7 mW/m2,with the most excellent performance.Observed by scanning electron microscope,the corrosion of the surface of the material coated with the graphene coating is alleviated,but after high temperature treatment,the surface structure of the coating is destroyed,and the corrosion resistance performance is not ideal.It is feasible to use coatings for surface modification of metal anodes,but a balance point should be sought between corrosion resistance and electricity generation performance.The above studies have verified the excellent performance of carbon nitride in the modification of MFCs anodes,and explored the application and modification of metal 3D anodes.The anti-corrosion treatment of foamed nickel anodes has achieved preliminary results,laying the foundation for the application of low-cost metal materials in MFCs.