Cathodic Properties Of Nitrogen-doped Metal-free Carbon-based Microbial Fuel Cells

Microbial fuel cells(MFCs)are a bioelectrochemical system,which has attracted considerable attention as a green biotechnology for the efficient extraction of energy from organic matter in wastewater.One of the bottlenecks for the large scale practical application of MFCs is the sluggish oxygen reduction reaction(ORR)at the cathode side.In order to improve the power generation of MFCs and the ORR efficiency of MFCs cathodes,in this study,the nitrogen(N)-doped metal-free carbon-based materials was prepared and the properties was measured.The samples were evaluated by XRD,BET,XPS,SEM,TEM and other characterizations,the mechanisms were analyzed and the electrochemical properties were tested.The results show that:(1)N-doped metal-free mesoporous carbon-based materials(NMPGCs)were prepared at different template additive amount.The content of NMPGCs was nearly the same,but the surface area and pore structure were very different.NMPGC-0.5 with large surface area,abundant mesoporous structure had better electrochemical activity.In CV and LSV tests,NMPGC-0.5 had the largest current density and exhibited the best electrochemical activity.The charge transfer resistance was the lowest,so that the long time stability of MFCs with NMPGC-0.5 cathode was better.The power density had only 9.2%of decline in the final cycle of operation,and it was low cost,environmental friendly.(2)N-doped metal-free biomass carbon-based materials(NBPGCs)were prepared by using cornstalks as carbon resourses and melamin as nitrogen resourses at different pyrolysis temperatures.The N content of NBPGCs was diferent from each other,as the pyrolysis temperature increased,the total N content decreased,but the ratio of graphitic N and oxidized N were increased.NBPGCs with large surface area,porous structure and N-defects could afford more active sites,improved the degree of graphitization and the conductivity.NBPGC-1000 had the largest current density in both CV and LSV tests.The calculated transfer number of NBPGC-1000 was 3.75,belonged to the less energy loss 4e-pathway.MFCs with NBPGC-1000 cathode had the highest output voltage(0.57V)and power density(1122mWcm-2),and had only 10.2%of decline in the final cycle,much better than Pt/C cathodes.Therefore,the as-prepared N-doped metal-free carbon-based materials could be applied in large-scale MFCs.The properties of N-doped metal-free carbon-based materials were better and it was low cost,environmental friendly,could provid new references for preparing efficient and stable ORR catalyst.