Preparation And Performance Of Carbon-based Non-precious Metal Oxygen Reduction Catalysts

Due to the scarcity of non-renewable resources and the air pollution caused by excessive use of petroleum resources,people urgently need green energy to solve the energy and environmental problems.Among many green energy,hydrogen energy has attracted people's attention because of its wide sources and high combustion calorific value.Proton exchange membrane fuel cell?PEMFC?is a device that converts hydrogen energy into electrical energy.The cathode oxygen reduction catalyst of PEMFC has a great influence on the whole system,so it is of great significance to study the cathode catalyst.At present,Pt based carbon materials and other precious metal catalysts have the best cathode performance in PEMFC,but the scarcity and high price of precious metals have seriously affected their commercial application.Therefore,researchers are committed to develop non noble metal catalysts to replace noble metal catalysts.At present,metal nitrogen carbon?M-N-C,in which M represents transition metals such as Fe,Co,Ni,Mn?is regarded as the most potential non noble metal oxygen reduction catalyst to replace Pt/C.However,there are still some problems in this kind of catalysts:most of them have high activity of oxygen reduction in alkaline medium,but their activity in acid medium is still not ideal,and some of them are not test by H₂O₂-fuel cell.At present,to prepare nitrogen doped carbon catalyst,it is necessary to add materials with high specific surface area such as carbon black as carbon source.In order to solve this problem,ZIF-8 after carbonization is chosen as the carbon material with super high specific surface.At the same time,a series of non-noble metal catalysts for oxygen reduction were prepared by simple synthesis method and act as cathode catalyst tested by PEMFC.?1?Using ferrocene as Fe source and ZIF-8 as carbon source,which are uniformly mixed by ball milling to obtain raw materials,and then sequentially pyrolyzed under in nitrogen and ammonia at 900?.The optimized sample Fe NC-1:30 has an onset potential of 0.95 V vs.RHE and half-wave potential of 0.78 V vs.RHE in acidic solution.In fuel cell test,Fe NC-1:30 catalyst has a current of 0.38 A cm^-2 at 0.7 V.?2?Using MIL-101?Fe? as Fe source and ZIF-8 carbon source,which are uniformly mixed by ball milling to obtain raw materials,and then sequentially pyrolyzed under in nitrogen and ammonia at 950?.Ammonia can provide nitrogen source.The optimized sample Fe NC-1:20 has an onset potential of 0.96 V vs.RHE and half-wave potential of 0.79 V vs.RHE in acidic solution.In fuel cell test,Fe NC-1:20 catalyst has a current of 0.34 A cm^-2 at 0.7 V.?3?Using NH₂-MIL-101?Fe? as Fe source and nitrogen source and ZIF-8 carbon source,which are uniformly mixed by ball milling to obtain raw materials,and then sequentially pyrolyzed under in nitrogen and ammonia at 950?.The optimized sample Fe NC-1:15 has an onset potential of 0.98 V vs.RHE and half-wave potential of 0.8 V vs.RHE in acidic solution.In fuel cell test,Fe NC-1:15 catalyst has a current of 0.51 A cm^-2 at 0.7 V and a maximum power of 895 mW cm^-2.