Defect-Engineered Fe3C@NiCo2S4 Nanospike Derived from Metal-Organic Frameworks as an Advanced Electrode Material for Hybrid Supercapacitors

The rational synthesis and tailoring of metal-organic frameworks (MOFs) with multifunctional micro/nanoarchitectures have emerged as a subject of significant academic interest owing to their promising potential for utilization in advanced energy storage devices. Herein, we explored a category of three-dimensional (3D) NiCo ₂S ₄ nanospikes that have been integrated into a 1D Fe ₃C microarchitecture using a chemical surface transformation process. The resulting electrode materials, i.e., Fe ₃C@NiCo ₂S ₄ nanospikes, exhibit immense potential for utilization in high-performance hybrid supercapacitors. The nanospikes exhibit an elevated specific capacity (1894.2 F g ^-1 at 1 A g ^-1), enhanced rate capability (59%), and exceptional cycling stability (92.5% with 98.7% Coulombic efficiency) via a charge storage mechanism reminiscent of a battery. The augmented charge storage characteristics are attributed to the collaborative features of the active constituents, amplified availability of active sites inherent in the nanospikes, and the proficient redox chemical reactions of multi-metallic guest species. When using nitrogen-doped carbon nanofibers as the anode to fabricate hybrid supercapacitors, the device exhibits high energy and power densities of 62.98 Wh kg ^-1 and 6834 W kg ^-1, respectively, and shows excellent long-term cycling stability (95.4% after 5000 cycles), which affirms the significant potential of the proposed design for applications in hybrid supercapacitors. The DFT study showed the strong coupling of the oxygen from the electrolyte OH ^- with the metal atom of the nanostructures, resulting in high adsorption properties that facilitate the redox reaction kinetics.