High Performance Microbial Fuel Cell Based On Two-Dimensional Layered Electrode

Microbial fuel cell（MFC）is a new energy battery that can realize energy conversion and production capacity.Compared with other fuel cells,lower power density and longer startup time are still the biggest bottlenecks in its practical application.As the carrier for the attachment of electricity-generating microbes,the anode directly affects the attachment speed,adhesion stability,and extracellular electron transfer efficiency of the electricity-generating bacteria on its surface.Therefore,starting from improving the power generation efficiency of MFC,choosing appropriate anode modification materials to carry out research is of great significance for improving the overall performance of MFC.The two-dimensional layered material represented by graphene,with its excellent specific surface area,electrical conductivity and biocompatibility,makes it a very promising anode modification material.In this paper,two-dimensional layered materials graphene and Ti₃C₂T_x MXene were selected to modify their hydrophilicity and capacitance through theoretical analysis and experimental design.The following two aspects have been specifically studied:（1）A super-hydrophilic electrode was prepared by dopamine-induced reduction of graphene oxide modified carbon cloth（rGO@PDA）and used as an anode for microbial fuel cells（rGO@PDA/CC）.Through simple and efficient structural modification,rGO@PDA/CC integrates the super hydrophilicity,bioadhesion of PDA and the electrical conductivity and biocompatibility of rGO.And the surface functional groups introduced by PDA effectively promote extracellular electron transport between bacteria and anode.Since the electro-producing bacteria can quickly attach to the anode surface,the startup time of rGO@PDA/CC MFC was shortened to 18 hours,while the startup time of rGO/CC MFC and CC MFC was 48 hours and 58 hours,respectively.The maximum power density of rGO@PDA MFC was 988 mW·m^-2,which was much higher than that of rGO/CC MFC(731mW·m^-2)and CC MFC(312 mW·m^-2).In addition,the decolorization rate of typical azo dye Congo red by rGO@PDA MFC can reach 89.7%within 24 hours,and the removal rate of chemical oxygen consumption（COD）reaches 77.8%within 96 hours.Characterization and analysis of Congo red degradation products by LC-MS technology,rGO@PDA MFC can convert Congo red macromolecules into small molecule products in a short time.These results were mainly due to the good biocompatibility and conductivity of the rGO@PDA anode and the stable biofilm on the anode surface.The synergistic effect of graphene and polydopamine effectively enhanced the overall power generation and waste reduction performance of microbial fuel cells.（2）A new three-dimensional structure MFC anode modification material（MXene/MnO₂）was designed by synergistically coupling two-dimensional MnO₂ nanosheets and MXene sheets.The MXene/MnO₂ composite had a three-dimensional sheet network structure with a specific surface area of 96.35 m²·g^-1.The three-dimensional structure of the sheet interconnection can form a conductive grid,providing more channels for electron transmission and its macroporous structure can also provide a larger colonization space for microbes.With its excellent pseudocapacitive properties,the MnO₂ improves the adhesion of bacteria on the anode surface and accelerates the electron transmission through a rapid redox reaction,MXene greatly enhances the conductivity of the anode and reduces the electron transmission resistance of MFC.And the power output of MXene/MnO₂/CC MFC was effectively increased.After assembling the MFC,it was observed that the maximum power density of MXene/MnO₂/CC was 760 mW·m^-2,much higher than that of MnO₂/CC MFC(483 mW·m^-2)and CC MFC(312 mW·m^-2).The decolorization rate of MXene/MnO₂/CC MFC to the typical azo dye Congo Red can reach 87.6%within 48 hours.The obtained MXene/MnO₂ not only ensured the stable structure of the nanocomposite,but also greatly promoted the electron transfer and ion diffusion in the nanocomposite.The strong synergistic effect of MnO₂ nanosheets and MXene effectively improves the overall performance of microbial fuel cells.