Study On Preparation And Performance Of Metalair Battery Cathode Catalyst

In today's society,the economy is constantly developing,which brings with it a series of environmental pollution problems,and is also facing an increasingly serious energy crisis.Therefore,renewable energy including wind energy,wave energy,solar energy and water energy has become an alternative energy source to traditional fossil fuels to achieve social goals of green,economic and sustainable development.In recent years,electric vehicles have developed rapidly.Metal-air batteries and fuel cells have great potential in the next generation of electric vehicles and hybrid vehicles.Due to the advantages of high theoretical energy density and specific capacity,environmental protection of materials,low production cost and high safety,metal-air batteries have attracted a large number of researchers to research and develop to improve the performance of metal-air batteries.The purpose is to make metal-air batteries be applied to people's daily life as soon as possible.Because the metal-air battery is composed of metal electrode,electrolyte and air electrode,the factors that affect the performance of the metal-air battery are also these three aspects.Among them,the most critical technology is to design an efficient and industrially produced air electrode,and the most important of the air electrode is an oxygen reduction(ORR)electrocatalyst.Therefore,for the industrial production and commercial application of metal-air batteries,on the one hand,it is necessary to develop and research catalysts with high activity and low production cost to improve the performance of air batteries;on the other hand,it is necessary to develop and research methods for the industrial preparation of catalysts in batches.This paper mainly studies the design and preparation of nano-catalysts for rechargeable zinc-air batteries and aluminum-air batteries,and does the following two tasks:(1)Developed a MOF(FeCo@NC+MOF)array grown on the surface of FeCo@NC porous carbon nanofibers as a dual-function catalyst for rechargeable zinc-air batteries.FeCo-doped nanofiber membranes were prepared by electrospinning,and array-shaped Co-MOFs were grown on the surface,followed by high-temperature carbonization,and FeCo@NC porous carbon nanofiber membranes supported by the array MOF were obtained.Reasonable optimization of performance improves the performance of rechargeable zinc-air batteries.Thanks to the unique three-dimensional multi-level porous structure,on the one hand,this structure can expose more active sites,at the same time,it is conducive to the rapid transport of reactive substances and generated substances;on the other hand,it is conducive to the rapid transfer of charges and electrons transportation.In addition,this nanofiber membrane catalyst has good flexibility and mechanical properties and can be directly used as an electrode material for air electrodes.The obtained FeCo@NC+MOF composite has excellent electrochemical properties.In alkaline electrolyte,the half-wave potential of the catalyst in the oxygen reduction reaction reaches 0.875V,which is superior to commercial platinum-carbon catalysts.At the same time,the stability and resistance to methanol are far superior to commercial platinum carbon catalysts.In the oxygen precipitation reaction,the overpotential of the FeCo@NC+MOF composite at a current density of 10 mA cm-2 is 410 mV,which is much smaller than the overpotential of 474 mV for commercial catalyst iridium oxide.In order to test the battery performance of the catalyst,we prepared the catalyst into a self-supporting air electrode without a binder and applied it to a rechargeable zinc-air battery.The assembled rechargeable zinc-air battery has an open circuit voltage of 1.45 V and a power density of 180 mW cm-2.The charge and discharge at a current density of 5,10,and 20 mA cm-2 were tested.The battery is stable in charge and discharge with almost no degradation in performance,far superior to commercial platinum-carbon catalysts.(2)Based on the limitation of the commercialization of catalysts,an important reason why it is difficult to commercialize metal-air batteries is to explore a method for catalysts to be prepared in batches.The formamide was used as a carbon source and a nitrogen source,and a metal salt was continuously added by heating under reflux to prepare a solid product,which was further carbonized to prepare a Co-N-C catalyst.In addition,the solution remaining after the solid is separated can be used as the mother liquor for the next reaction for repeated recycling.Using this method,by adjusting the reaction temperature and the amount of metal salt added,we have initially explored a method that can prepare catalysts in batches.At the same time,the obtained Co-N-C catalyst material has excellent electrochemical performance.In alkaline electrolyte,the half-wave potential of the catalyst in the oxygen reduction reaction reaches 0.90V,which is far superior to commercial platinum-carbon catalysts.We then applied the Co-N-C catalyst material to a homemade aluminum-air battery.The assembled aluminum-air battery can achieve an open circuit voltage of 1.77V and a power density of 200 m W cm-2.The discharge performance was tested at a current density of 10,20,50,100 mA cm-2,and the current discharge was stable and almost no attenuation.