Preparation Of ZIF-derived Porous Carbon Nanofiber Supported Pt And PtCo Catalysts And Their Oxygen Reduction Performance

The proposal of the"double carbon"goal and the rapid consumption of non-renewable fossil energy make the development and utilization of clean,green and renewable energy urgent.In recent years,as typical new energy technologies,fuel cells and metal-air batteries have been widely studied due to their high energy,high efficiency,and green environmental protection.The kinetically slow oxygen reduction reaction（ORR）at the cathode is a key factor determining the performance of these devices.Platinum-based catalysts are still the best ORR electrocatalysts.However,due to the scarcity and high price of platinum-based materials,the large-scale promotion of fuel cells and metal-air batteries is limited.For the most widely used commercial platinum-carbon（Pt/C）catalysts,how to maximize the utilization of Pton the basis of improving its activity and stability has become a research hotspot.In this paper,a series of nano-Ptcrystal/porous carbon fiber composites were prepared by electrospinning and high-temperature carbothermic reduction using zeolite imidazolate framework（ZIF）materials as self-sacrificial templates and steric confinement agents.By adjusting the type of ZIF,the amount of Ptprecursor added and the electrospinning process parameters,the material composition and structure were regulated;and the relationship between the material composition,structure and electrocatalytic performance was systematically studied,and obtained Pt-based nanocatalysts with outstanding electrocatalytic performance.The main findings of this paper are as follows:（1）Starting from zinc-based ZIFs,porous carbon nanofiber composites （ZIF@Pt/CNFs）anchored with Ptnanoparticles were successfully prepared.The influence of the amount of precursor reactants on the composition and structure of the material was studied,and the electrocatalytic performance of the material was systematically studied.ZIF@Pt/CNFs,with large specific surface area,abundant pore structure and hetero-element doping,and uniformly dispersed low-content Ptnanoparticles,exhibit excellent catalytic activity as oxygen reduction electrocatalysts(half-wave potential of 0.863 V,the limiting diffusion current density is 4.97 mA cm^-2).The mass activity of Ptin ZIF@Pt/CNFs at 0.9 V(216.27 mA mg _Pt^-1)was 5times higher than that of commercial Pt/C.It is worth noting that the ZIF@Pt/CNFs catalyst exhibits impressive stability with a half-wave potential only 8 mV smaller than the initial value after 30,000 cycles.（2）On the basis of the material preparation in（1）,the doping of metallic cobalt in Pt-based carbon nanofibers（PtCo/CNFs）was realized by introducing a small amount of cobalt ions into ZIF.Cobalt doping enhances the degree of graphitization and electrical conductivity of carbon materials,and improves the electronic structure of Ptby alloying,so the PtCo/CNFs catalyst exhibits high ORR performance,such as the half-wave potential is 0.842 V,the limiting diffusion current density increases to 5.85 mA cm^-2.In addition,the PtCo/CNFs catalyst also showed high stability.After 30,000 cycles,the half-wave potential was only 11 mV lower than the initial value,and the long-term stability test was better than that of the commercial Pt/C catalyst.