Study On Cathode Properties Of Nitrogen Doped MoS 2 /C Composite Microbial Fuel Cells

Owing to the exhaustion of non-renewable resources(such as fossil fuels)and the aggravation of environmental problems(such as the global climatic warming),the exploration of the alternative energy is required to optimize the present energy system.Microbial fuel cells(MFCs),as a new type of energy recovery technology,have attracted wide attention,which can generate electricity while treating wastewater.However,the problems such as the low voltage output and the high cost of the existed cathode catalyst limit the extensive usage of MFCs.Thus,it is urgent to develop a new cathode catalyst with the characters of high-efficient and low-cost.In this study,N-MoS2/C cathode catalysts are prepared by the aqueous evaporation-induced self-assembly process and carbonization method,using melamine(carbon and nitrogen sources),thiourea(sulfur source),ammonium molybdate(molybdenum source)and F127(the soft template).The N-MoS2/C composites are characterized by XRD,XPS,BET,SEM,TEM and other physical or chemical measurements.The electrochemical properties are evaluated by using CV,LSV and RDE tests.The correlation of active components,structure and the ORR activity of N-MoS2/C are detected by tuning the heating temperature(800-1000?).It can be discovered that with the increase of the heating temperature,the crystallization of MoS2 becomes higher.During the process of removing the F127 by carbonization method,abundant active centers are exposed,which can provide plenty of active sites for ORR.The sufficient reaction between the active sites and oxygen can facilitate the ORR by improve the oxygen permeation.MFCs with N-MoS2/C-900 cathode obtains the maximum power density(0.815 W m-2),which is higher than that of the commercial Pt/C(10 wt.%).After a long-time operation(1700 h),the power density of MFC with N-MoS2/C-900 cathode only declines 1.23%,which shows good durability in long-time running.The dominant ORR pathway of N-MoS2/C-900 follows the four-electron O2 reduction,which can be attributed to the synergy between the lattice defects,pyridinic N,graphitic N and Mo-Nx species in N-MoS2/C-900 catalyst.N-MoS2/C/CNT-x(x=600,700,800,900?)composite materials are also synthesized using the same sources and methods,except for adding CNT(10-20 nm)during the mechanical mixing process.Melamine,thiourea and ammonium molybdate can be used as precursor in the process of the introduction of F127 and CNT.The obtained N-MoS2/C/CNT-800 possesses the largest BET specific surface area of 121.98 m2 g-1 among all N-MoS2/C/CNT composites.The maximum power density of 0.824 W m-2 can also be deserved by MFCs with N-MoS2/C/CNT-800 cathode,whose high catalytic activity can be generally attributed to the enhancement of conductivity.During the long-time operation,MFCs with N-MoS2/C/CNT-800 cathode also exhibits long-term stability.Both the prepared N-MoS2/C and N-MoS2/C/CNT composites show outstanding performance in MFCs,which can be considered as ideal candidates to replace the use of Pt/C in MFCs.