Synthesis And Bifunctional Oxygen Electrocatalytic Performance Of Fe-based ZIFs Derived Carbon Materials

The kinetics of oxygen reduction reaction（ORR）and oxygen evolution reaction（OER）on the air electrode in zinc-air batteries is slow,which seriously reduces the actual performance of rechargeable zinc-air batteries.Therefore,efficient bifunctional oxygen electrocatalysts are needed to catalyze ORR/OER.Zeolitic imidazolate frameworks（ZIFs）derived carbon materials show great potential in electrochemistry because of their low cost,flexible structure,abundant porosity and nitrogen content.In this paper,Zn-ZIFs was used as precursors for the preparation of efficient bifunctional oxygen catalysts,and a series of Fe-based carbon materials were synthesized.The structure and composition of the prepared catalysts were evaluated by XRD,Raman,SEM,XPS,etc.Their bifunctional oxygen catalytic performance and application in znic-air batteries were studied by electrochemical tests.The main results are as follows.Firstly,one-dimensional carbon nanofibers doped with Fe₂O₃ nanoparticles were synthesized by electrospinning-impregnation-calcination method.It was found that ORR catalytic activity of the carbon materials could be significantly improved by the addition of iron.In alkaline electrolyte,the catalyst with a Zn/Fe mole ratio of 12 exhibited the best ORR performance,a half-wave potential reached 0.905 V.In addition,its ORR performance was also comparable to or even better than that of Pt/C in neutral and acidic electrolytes.Secondly,Fe,Ni co-doped one-dimensional carbon nanofibers were synthesized by electrospinning-calcination method.Results showed that the addition of Ni could improve the OER catalytic activity of Fe-based carbon materials.The porous structure could be formed during the pyrolysis process of ZIFs,which significantly increased the specific surface area of carbon materials.Finally,ZIFs-derived Fe,Ni co-doped two-dimensional carbon nanosheets were prepared by a simple dynamic precipitation-calcination method.It was found that the synergistic effect of Fe and Ni could improve the OER catalytic activity of the catalyst.The catalyst with a Fe/Ni mole ratio of 2 exhibited the optimal ORR/OER catalytic activity,the voltage difference（ΔE）was low to 0.758 V.Besides,rechargeable zinc-air batteries based on the prepared catalysts also showed high power density and good charge-discharge cycle stability.