Preparation And Device Application Of Hierarchically Structure Fe-N-C Oxygen Reduction Catalyst

Fuel cells and zinc-air batteries have promising applications as energy conversion devices,but the sluggish kinetics of the cathode require catalysts for catalysis.Among various cathode catalysts,M-N-C is considered as a catalyst with good application prospects.However,many active sites in M-N-C catalysts are buried,resulting in poor catalytic activity.The catalyst with hierarchical pore structure can not only expose more active sites,but also help to improve the mass transfer effect of the catalyst,which has a better effect on the catalytic effect of the M-N-C catalyst,and when it is applied to the device,it has better device performance and more excellent stability.Based on the above control strategies,the main research contents of this paper are as follows:（1）Molten salt method to construct highly active oxygen reduction catalysts.Based on increasing the density of active sites and improving the mass transfer capacity of the catalyst,a Fe-N-C oxygen reduction catalyst with a hierarchical porous structure was synthesized using ZIF8 as carbon and nitrogen sources,glucose and sodium chloride as pore formers.By optimizing the experimental parameters such as pyrolysis temperature,heating rate,metal content,and the addition method and content of sodium chloride,the catalyst with the best performance was obtained.Its half-wave potential reaches 0.813 V under acidic conditions,which is close to 20 wt%of commercial Pt/C.The peak power density in the proton exchange membrane fuel cell is 427 m W cm^-2.Meanwhile,the half-wave potential is close to 0.93 V under alkaline conditions,which is much higher than that of 20 wt%commercial Pt/C.In the potentiostatic test,80%of the catalytic activity is still maintained after 100,000 s with strong stability and potential for commercial applications.（2）Self-assembly to construct highly active bifunctional catalysts.Based on the different catalytic properties of different catalytic materials,fully combining the characteristics of different materials,a self-assembly strategy was adopted to composite Ni Fe hydrotalcite and hierarchical porous carbon,and self-assembly formed a bifunctional catalyst with both high ORR catalytic effect and OER catalytic performance.The ORR half-wave potential of the catalyst reaches 0.901 V,and the OER potential at a current density of 10 m A cm^-2 is 1.578 V.The potential difference between the two is only 0.677 V,which is lower than most of the non-precious metal catalysts that have been reported.After 50,000 s,82%of the catalytic activity is still maintained,and after 1000 CV cycles,the potential of（Fe Co）HPNC@LDH at a current density of 10 m A cm^-2 is only 0.03 V lower than that before the initial cycle.Meanwhile,in the zinc-air battery test,a peak power density of 148 m W cm^-2 was exhibited.The voltage of（Fe Co）HPNC@LDH did not change significantly after 100 hours of charge and discharge,indicating that the catalyst（Fe Co）HPNC@LDH has high catalytic performance and stabilization effect,and has a promising commercial application.