Preparation Of Non-Precious Metal Oxygen Reduction Catalysts By ZIF-8 And MIL-53

Fuel cell is a device that can directly convert chemical energy in fuel into electrical energy.Being a kind of green energy is considered as one of the important means to solve the energy problem in today's society.However,fuel cells are currently difficult to commercialize due to their high cost.They are only used in military and aerospace and other special fields.Civilian applications such as Proton exchange membrane fuel cell vehicles are still in their infancy,but they have been developing rapidly in recent years.However,today,proton exchange membrane fuel cells still use a large amount of precious metal platinum as a catalyst,which accounts for about 30% of the cost of fuel cells.Therefore,the development of non-precious metal catalysts to replace the expensive platinum catalysts is an important research direction for reducing the cost of fuel cells and accelerating the commercialization of fuel cells.In this dissertation,basis on the metal-organic framework material(MOF),a number of MOF materials containing different metals were synthesized by reference.The MOF was mixed and doped by ball milling to obtain non-noble metal oxygen reduction catalysts with high oxygen reduction activity in acidic environment.A variety of physical and electrochemical characterization methods were used to study the catalyst in detail,and the effects of the catalyst components on the oxygen reduction activity and stability were discussed.The specific work is as follows:1.Two different MOF materials,MIL-53(Fe)and ZIF-8,were synthesized by hydrothermal method and ball milling method respectively.Iron-containing MIL-53(Fe)was used as the iron source,and mixtures with different proportions were made by high-speed ball milling.The mixture was pyrolyzed at high temperature and the sample was doped with ammonia using ammonia as a nitrogen source.The final sample has a very high oxygen reduction activity in the acidic solution,and the prepared fuel cell membrane electrode has a good open circuit potential.The difference in performance mainly comes from the iron content and nitrogen content in the sample.2.The CoNC catalyst and FeCoNC bimetallic catalyst were prepared on the basis of ZIF-8 with MIL-53(Fe)and MIL-53(Co)as the iron source and the cobalt source respectively.The addition of cobalt greatly improves the stability of the catalyst,and the ratio of cobalt and iron has a great influence on the performance and stability of the catalyst.Studies have found that the synergistic action of cobalt and iron can protect the oxygen reduction active sites.3.CoNC was doped with nitrogen and iron with phenanthroline and ferrous acetate.The oxygen reduction activity after doping was explored to further demonstrate the effect of metal nitrides on catalyst activity.