Power Generation Performance Of Fe (Cu)-N Co-Doped Porous Carbon In Microbial Fuel Cells

The development of human beings is accompanied by the double crisis of energy and water pollution.Microbial fuel cells（MFCs）technology is one of the effective solutions to these problems.At present,the slow oxygen reduction reaction（ORR）process on the cathode is a shackle limiting the development of MFCs,and Pt metal with excellent performance is expensive and unstable.Therefore,it is necessary to develop a more efficient,stable and cheap catalyst to replace the traditional Pt/C and promote the evolution of microbial fuel cells.In this paper,based on the research of nitrogen-doped porous carbon materials,iron-nitrogen co-doped porous carbon material（Fe-Np C）and iron-copper-nitrogen co-doped porous carbon（Fe_xCu_y-NC）series catalysts were prepared.The morphology and surface properties of the catalysts were analyzed by a variety of characterization methods.The main factors affecting the catalytic activity of ORR in the catalysts were obtained,and the ORR performance of the material and the power generation and sewage treatment capacity of the battery applied in MFCs were evaluated by electrochemical and hydrochemical tests,respectively.The specific research content is as follows:（1）The iron-nitrogen co-doped porous carbon（Fe-NpC）catalysts with high specific surface area were synthesized by salt template method,adding accessible histidine.Due to the high nitrogen content and carboxyl structure of histidine,it was able to construct developed pore structure and highly dispersed metal sites under strong alkaline environment.The electrochemical characterization results showed that Fe-Np C obtained the highest electrochemical activity in all p H conditions compared with Mn-Np C,Ni-Np C and non-metal Np C.The half-wave potentials of 0.902 V,0.705 V and 0.777 V（vs.RHE）were measured in alkaline,neutral and acidic environments,respectively.This performance was better than or close to the commercial Pt/C,and higher than most of the current reports.At the same time,the Fe-Np C-MFC cell possessed high open-circuit voltage（775 m V）and maximum power density(1793±77 m W m^-2).The output voltage of this battery only decreased by 6.0%after 430 hours of continuous operation,and the chemical oxygen demand removal rate reached 90.3±4.3%.This study elucidated that the excellent ORR performance and stability of Fe-Np C was related to its internal single-atom dispersed and tightly bounded Fe-N₄ structure.The practical application of Fe-Np C catalyst in wastewater treatment by MFCs was feasible.（2）Using ferrous acetate,copper acetate,homobenzoic acid and dicyandiamide as precursors,a series of iron-copper-nitrogen co-doped porous carbon（Fe_xCu_y-NC）catalysts were synthesized by one-step pyrolysis method.The effects of different metal addition ratios on the phase composition and ORR performance of the catalysts were investigated.The electrochemical characterization results displayed that Fe₂Cu₂-NC had similar properties to Pt/C under alkaline and neutral conditions,and the half-wave potentials reached 0.858 V and0.624 V（vs.RHE）,respectively.Meanwhile,both electron transfer numbers were close to four.With the increase of the amount of a single metal,the catalyst performance first increased and then decreased.Meanwhile,Fe₂Cu₂-NC enabled to provide an open-circuit voltage of 710 m V and a maximum power density of 1295±67 m W m^-2 in MFCs,and the cell has a coulomb efficiency of 10.7±0.8%.This study illustrated that the optimal performance is achieved when the ratio of iron and copper is 1:1.This strategy can effectively regulate the morphology and structure of the catalyst and increase the content of active nitrogen,so as to further improve the power generation capacity and wastewater treatment capacity of MFCs.