Silver citrate engineered NiCo2S4/MOF-derived oxide@carbon frameworks for high-energy hybrid supercapacitors

Abstract

Metal–organic frameworks (MOFs) offer a versatile platform for designing high-performance supercapacitor electrodes, but their poor intrinsic conductivity and structural instability limit practical application. Here, we report an silver-citrate-modified NiCo₂S₄@calcined-MOF composite derived from a trimetallic NiCoZn-MOF template for hybrid supercapacitor electrodes. The parent NiCoZn-TPA MOF is first calcined to form a porous NiO/CoO/ZnO/carbon framework that provides mechanical robustness and enhanced conductivity. NiCo₂S₄ nanoparticles are then grown in situ on this scaffold, followed by the incorporation of silver-citrate to introduce additional redox-active sites and highly conductive Ag pathways. Structural and chemical characterization confirms the successful formation of a plate-like oxide-carbon framework uniformly decorated with NiCo₂S₄ and silver-citrate nanoparticles. The optimized composite (A4, 60 wt% NiCo₂S₄@calcined-MOFs/40 wt% silver-citrate) delivers a high specific capacity of ∼836C g⁻¹ at 0.5 A g⁻¹ in 1 M KOH. An asymmetric device based on A4//activated carbon achieves an energy density of 94 Wh kg⁻¹ at 577 W kg⁻¹, while maintaining high-rate capability and 82% capacitance retention after 5000 cycles with 98% coulombic efficiency. Dunn analysis reveals combined faradaic and capacitive contributions, highlighting the hybrid charge-storage behavior of this MOF-derived multicomponent electrode architecture.