Sulfurization-induced mesoporous hollow NiCo2S4 polyhedrons from ZIFs for high-performance asymmetric supercapacitors with superior electrochemical stability

This study introduces an innovative approach to deriving highly mesoporous hollow NiCo₂S₄ polyhedrons from zeolitic imidazolate frameworks (ZIFs), with a focus on electrochemical efficiency. Synthesized via a straightforward coprecipitation route, the NiCo-ZIFs were transformed directly into bimetallic sulfides using thioacetamide as a sulfur source, allowing gradual dissolution of the ZIF’s inner layers. This process formed hollow polyhedrons with retained morphology and significantly enhanced mesoporosity, confirmed by BET analysis, showing a high surface area of 165 m²/g. Electrochemical characterization revealed a remarkable specific capacitance of 1357 F g⁻¹ at 1 A g⁻¹ and 91.1 % retention after 5000 cycles, showcasing enhanced electrochemical stability, supported through ex-situ XRD and SEM analysis. In a two-electrode configuration with biomass-derived reduced graphene oxide (rGO) as the counter electrode, the NiCo₂S₄ delivered a maximum energy density of 58.5 Wh kg⁻¹ and a power density of 3.44 kW kg⁻¹. This high-performance behaviour led to the successful fabrication of an asymmetric supercapacitor, demonstrating the practical applicability and robust reliability of the NiCo₂S₄ polyhedrons for next-generation energy storage solutions in real-world applications.