Fabrication of solid-state symmetric supercapacitor using g-C 3 N 4 /NiS nanocomposites with real-time LED illumination capability

A simple hydrothermal technique was employed to prepare graphitic carbon nitride (g-C3N4)/nickel sulfide (NiS) nanocomposites with 2–6 wt% NiS loading for supercapacitor applications. The optimized synergistic interaction between layered g-C3N4 and sponge-like NiS enhances charge transport, active-site availability, and electrochemical stability. Structural characterization confirmed the integration of hexagonal NiS with g-C3N4, while FE-SEM revealed interconnected sheet-like/spongy architectures favorable for ion diffusion and electrolyte penetration. The g-C3N4/NiS-6% nanocomposite delivered a specific capacitance of 969.90 F/g at 0.5 A/g with 100% retention after 500 cycles in 3 M KOH. The fabricated solid-state symmetric supercapacitor (SSC) retained 94.5% capacitance after 10,000 cycles and exhibited 274.26–55.94 F/g at 0.5–5 A/g. The SSC successfully powered red, green, and blue LEDs, demonstrating its potential for durable and cost-effective solid-state energy storage.