Synthesis of Fe3C/VN/C composites through pyrolysis mixture of iron-vanadium precursor and melamine in inert gas for a supercapacitor electrode

Vanadium nitride (VN) has attracted significant attention as a promising electrode material for supercapacitors mainly owing to its high theoretical specific capacitance and broad electrochemical stability window. However, poor cycling stability caused by dissolution in alkaline electrolyte largely restricts its practical applications. Herein, a series of heterojunction Fe₃C/VN/C-x composites were synthesized via a one-step pyrolysis strategy for pyrolysis mixture of iron-vanadium precursor and melamine at 700 °C for 2 h. Among the series, the optimized Fe₃C/VN/C-2 exhibits a high specific capacitance of 291.2 F g^-1 at 0.5 A g^-1, which is 2.7 times higher than pristine VN with 108.3 F g^-1. Moreover, the Fe₃C/VN/C-2 enables asymmetric supercapacitor device (Ni(OH)₂||Fe₃C/VN/C-2) achieving a high energy density of 14.9 Wh kg^-1 with high power density of 400.1 W kg^-1 and a high power density of 3998.6 W kg^-1 with an energy density of 6.2 Wh kg^-1, and retaining 92.7 % of its initial capacitance after 10,000 cycles (17.2 F g^-1). The enhanced electrochemical performance of Fe₃C/VN/C-2 is attributed to the synergistic effect of the heterojunction and carbon matrix, which suppress vanadium dissolution and accelerate charge transfer kinetics.