Hollow Carbon Nanofibers with Inside-outside Decoration of Bi-metallic MOF Derived Ni-Fe Phosphides as Electrode Materials for Asymmetric Supercapacitors

[Display omitted] •Bi-metallic MOF-derived (Ni-Fe)-P-C@HCNFs and FePC@HCNFs are obtained as positive and negative electrodes of ASC.•Co-existence of redox-active bi-metallic phosphide at the inside and outside of HCNFs improves redox kinetics.•The (Ni-Fe)-P-C@HCNFs showed a high specific capacitance of 1392 F g−1 at 1 A g−1.•As fabricated ASC device shows a maximum energy density of 62.7 W h kg−1 at 8.23 kW kg−1 of power density. Bi-metallic metal–organic framework (MOF) generated phosphides within and outside the hollow carbon nanofibers (HCNFs) show remarkable potential for energy storage owing to their improved conductivity and high specific capacitance. A novel approach is used to synthesize (Ni-Fe)-P-C on the outer and inner surfaces of HCNFs. The synthesized material's substantial electrochemical performance is owing to the co-existence of numerous Ni and Fe-based redox-active species with porous carbon and open channels from MOF-derived Carbon at HCNFs for fast electrolyte ions/electron diffusion. Consequently, the (Ni-Fe)-P-C@HCNFs electrode has a high specific capacitance of 1392 F g−1 at 1 A g-1 and good cycling stability, with capacitance retention of approximately 89 % at 25 A/g. Moreover, after 10,000 cycles, the asymmetric supercapacitor (ASC): (Ni-Fe)-P-C@HCNFs//FePC@HCNFs has an optimal energy density of 62.7 Wh kg−1 and a power density of 8238.2 W kg−1, with cycling stability of 92.4 percent at a high current density of 25 A g-1.