Preparation And Electrochemical Properties Of Non-platinum-based Oxygen Reduction Catalysts Assisted By Mechanochemical Method

Fuel cells are essential devices for hydrogen energy applications,as they can directly convert chemical energy into electrical energy.Anion exchange membrane fuel cells（AEMFCs）are particularly noteworthy due to their mild electrolyte environment and potential cost reduction through the use of alloy bipolar plates and non-noble metal-based catalysts.As a result,AEMFCs have gained widespread attention,and their associated technologies have rapidly developed in recent years.To ensure the practicality of anion exchange membrane fuel cells,it is crucial to investigate cost-effective methods for synthesizing catalysts that are both green and scalable.This thesis focuses on the use of mechanochemical methods to prepare high performance,non-platinum-based oxygen reduction catalysts for cathodes.The resulting catalysts show promising results for use in anion exchange membrane fuel cells.The specific research content,including the incorporation of mechanochemical methods into the preparation of cathode oxygen reduction catalysts,is as follows:（1）Precursors of iron-doped zeolite imidazolium ester-based metal organic framework material with high specific surface area were prepared by mechanochemical method,and then carbonized at high temperature to prepare Fe-N-C type catalysts with high oxygen reduction activity.The effects of different iron-based precursors and different iron loading levels were investigated.It was selected that the catalyst prepared from ferrous chloride tetrahydrate under the condition of n _{Zn O}:n _Fe=15:1 had the highest nitrogen doping level and Fe-N_x active sites,and its oxygen reduction reaction half-wave potential under alkaline conditions reached 0.890 V（vs.RHE）.On this basis,the surface charge distribution of the catalyst is regulated by doping with heteroatoms to optimize the adsorption ability of oxygen intermediates and further enhance the catalytic activity of oxygen reduction The final prepared Fe-B-N-C catalyst has an oxygen reduction reaction half-wave potential of 0.900V（vs.RHE）under alkaline conditions.After 10000 cycles of accelerated aging test,the half-wave potential has no significant attenuation,exhibiting superior oxygen reduction activity and stability.（2）A silver-based oxygen reduction catalyst Ag-Cu Mn O_x/C（L）was obtained by rapidly preparing Cu Mn O_x/C carrier using mechanochemical methods under solvent-free conditions and further loading silver nanoparticles,exhibiting excellent membrane electrode assembly testing performance for anion exchange membrane fuel cells.The synthesis process was conducted under mild conditions and the overall experiment was conducted under normal temperature and pressure.The interaction between silver and copper manganese oxides enhanced the catalyst’s oxygen adsorption capacity and catalytic activity for oxygen reduction reactions under alkaline conditions,the half-wave potential for the oxygen reduction reaction can reach 0.836 V（vs.RHE）.After undergoing 4000 cycles of accelerated aging testing,the half-wave potential decreases by approximately 16 m V.The anion exchange membrane fuel cell membrane electrode assembly,which utilizes Ag-Cu Mn O_x/C（L）as the cathode catalyst,has been successfully implemented with a single battery peak power density of 0.87 W cm^-2,and its current density at 0.65 V reaches 0.82 A cm^-2,demonstrating satisfactory performance.