High-activity and stability graphite felt supported by Fe, N, S co-doped carbon nanofibers derived from bimetal-organic framework for vanadium redox flow battery

•Bimetal-organic framework derives Fe, N, S co-doped carbon nanofibers (Fe-N/S-CNFs).•In-situ growth enables Fe-N/S-CNFs uniform distribution and high stability on graphite felt.•GF@Fe-N/S-CNFs has abundant active sites, large specific surface area, and good stability.•GF@Fe-N/S-CNFs exhibits excellent catalysis for both VO2+/VO2+ and V2+/V3+ redox reactions.•Efficiency and cycling stability of the modified battery are significantly improved. High energy efficiency and cycle stability have always been the focus of research on vanadium redox flow battery (VRFB). It is noted that metal–organic framework (MOF) has many advantages due to porosity, controllable structure, and functional modification. Therefore, in this paper, a composite electrode with Fe, N, S co-doped carbon nanofibers in situ supported on graphite felt surface (GF@Fe-N/S-CNFs) was prepared by using bimetal-organic framework as precursor. GF@Fe-N/S-CNFs possess large specific surface area, abundant active centers, and high electrical conductivity, which exhibits excellent electrocatalytic activity for both VO2+/VO2+ and V2+/V3+ redox reactions. At 200 mA cm−2, energy efficiency and voltage efficiency of the modified battery using GF@Fe-N/S-CNFs are 71.7 % and 75.8 %, respectively, which are 9.7 % and 10.6 % higher than those of blank battery. Modified battery can still run smoothly at high current density of 300 mA cm−2. In addition, energy efficiency holds excellent steady during 350 charge–discharge cycles at 150 mA cm−2. Hence, this work brings a promising vision of MOF derivant for high-performance electrode of VRFB.