Phase Modulation and Electrochemical Behavior of Fe₃Mo₃C/Mo₂C Composite Nanofibers as Supercapacitor Negative Electrodes

The advancement of negative electrode materials is essential for enhancing the performance of supercapacitors. Fe–Mo-based bimetallic carbide presents significant potential as a supercapacitor negative electrode material. In this study, Fe 3 Mo 3 C/Mo 2 C composite nanofiber was synthesized using the electrospinning method followed by high-temperature carbonization. As-prepared composite nanofibers consist of two phases: Mo 2 C nanoparticles embedded within the nanofiber and a block-like dispersion of the Fe 3 Mo 3 C phase. The Mo 2 C-dominated Mo 2 C/Fe 3 Mo 3 C-900 electrode shows an optimal specific capacitance of 354.9 F g –1 at 1 A g –1, notably exceeding that of the Fe 3 Mo 3 C-dominated Fe 3 Mo 3 C/Mo 2 C-900 electrode (253.2 F g –1 ). This advancement can be ascribed to the enhanced textural characteristics and lower resistance. The assembled NiCo 2 O 4 //Mo 2 C/Fe 3 Mo 3 C-900 device yields an energy density of 54.6 Wh kg –1 when the power density is 850 W kg –1 . On the other hand, the NiCo 2 O 4 //Mo 2 C/Fe 3 Mo 3 C-900 ASC device retained 67% of its capacitance after 5000 charge–discharge cycles, underperforming that of the NiCo 2 O 4 //Fe 3 Mo 3 C/Mo 2 C-900 (78%). This suggests that composite nanofiber with Mo 2 C as the main phase exhibits superior specific capacitance, while the bimetallic carbide Fe 3 Mo 3 C presents higher conductivity, which further improves its electrochemical stability. In short, the as-designed Fe 3 Mo 3 C/Mo 2 C composite nanofibers present promising negative electrode features for energy storage applications.