Temperature-controlled synthesis of MOF-derived Ni₃S₂/C nanocomposites for high-performance supercapacitors

Supercapacitors have emerged as a crucial class of energy storage devices due to their high power density and long cycle life. However, the development of electrode materials that combine high specific capacitance and robust stability remains a challenge. In this work, two-dimensional (2D) Ni-based metal-organic frameworks (Ni-MOFs) were employed as precursors to synthesize Ni₃S₂ nanoparticles embedded within porous carbon nanosheets via a straightforward pyrolysis-vulcanization process. By systematically adjusting the auxiliary ligand in the MOF precursor and the subsequent calcination temperature (600, 800, and 1000 °C), the composition and morphology of the final materials were effectively tuned. The sample derived from Ni-MOF-a at 1000 °C (Ni-MOF-a@S10) exhibited optimal electrochemical performance, delivering a high specific capacitance of 497 F g^-1 at 0.5 A g^-1 and an outstanding cycling stability with 76.9% capacitance retention after 3000 cycles at 10 A g^-1. Kinetic analysis revealed that the charge storage was primarily governed by a surface-capacitive mechanism, which facilitated excellent rate capability. Furthermore, an asymmetric supercapacitor assembled with Ni-MOF-a@S10 as the positive electrode demonstrated a high power density of 1128.56 W kg^-1. This study not only presents a high-performance electrode material but also validates a versatile strategy for designing MOF-derived nanostructures for advanced energy storage applications.