Preparation of F and N Co-Doped Fe-N-C Catalyst and Evaluation of its Oxygen Reduction Performance

The problems of underdeveloped pores and high electrochemical impedance of oxygen reduction reaction (ORR) catalysts need to be urgently addressed. Heteroatoms F and N are doped on precursor Fe-zeolitic imidazolate framework (ZIF)-8 to increase the activity of Fe-ZIF-8-derived porous carbon materials and a noble metal-free high-activity ORR catalyst F-N/FeNC with 3D interconnected porous structure and high conductivity is successfully prepared. Experiments show that the synergistic effect of C-F ionic bonds, pyridinic-N, pyrrolic-N, graphitic-N, FeNx sites, and C-F semi-ionic bonds in F-N/FeNC can improve the ORR activity of the F-N/FeNC. The developed F-N/FeNC is advantageous with excellent specific surface area, ultra-high electrical conductivity, and extremely high ORR mass transfer efficiency. As such, the F-N/FeNC has a high onset potential of 0.95 V (vs RHE) and a half-wave potential of 0.84 V (vs RHE), implying excellent ORR performance even better than commercially available Pt/C catalyst. In addition, the carefully prepared F-N/FeNC demonstrated higher long-term durability and excellent resistance to methanol influence compared with commercially available Pt/C catalyst. The developed strategy provides new insights into heteroatom-doped metal-organic frameworks as a precursor of ORR catalysts.