This study presents the synthesis of Co₃O₄-g-C₃N₄ nanocomposites using the hydrothermal method and evaluates their performance as supercapacitor electrodes. The hydrothermal method effectively produced graphitic carbon nitride (g-C₃N₄) polymers and Co₃O₄ composites. The weight percentage of g-C₃N₄ nanoparticles significantly influenced the electrochemical performance of the Co₃O₄-g-C₃N₄ composite. The composite with 150 mg of g-C₃N₄ nanoparticles exhibited a specific capacitance of 198 F/g. The optimized electrode, activated carbon, and polyvinyl alcohol gel with potassium hydroxide were used to develop an asymmetric supercapacitor. At a current density of 5 mA/cm², the asymmetric supercapacitor demonstrated exceptional energy storage capacity with remarkable energy density and power density. The device retained great capacity over 6,000 galvanostatic charge–discharge (GCD) cycles, with no rise in series resistance following cyclic stability. The columbic efficiency of the asymmetric supercapacitor was also high. The study also investigated the structural and morphological properties of the nanocomposites using XRD, XPS, FESEM, and TEM analyses. The results showed that the composite with 150 mg of g-C₃N₄ nanoparticles had a good specific capacitance and enhanced electrochemical performance. The study concludes that the Co₃O₄-g-C₃N₄ composite electrode is a viable material for energy storage applications.This study presents the synthesis of Co₃O₄-g-C₃N₄ nanocomposites using the hydrothermal method and evaluates their performance as supercapacitor electrodes. The hydrothermal method effectively produced graphitic carbon nitride (g-C₃N₄) polymers and Co₃O₄ composites. The weight percentage of g-C₃N₄ nanoparticles significantly influenced the electrochemical performance of the Co₃O₄-g-C₃N₄ composite. The composite with 150 mg of g-C₃N₄ nanoparticles exhibited a specific capacitance of 198 F/g. The optimized electrode, activated carbon, and polyvinyl alcohol gel with potassium hydroxide were used to develop an asymmetric supercapacitor. At a current density of 5 mA/cm², the asymmetric supercapacitor demonstrated exceptional energy storage capacity with remarkable energy density and power density. The device retained great capacity over 6,000 galvanostatic charge–discharge (GCD) cycles, with no rise in series resistance following cyclic stability. The columbic efficiency of the asymmetric supercapacitor was also high. The study also investigated the structural and morphological properties of the nanocomposites using XRD, XPS, FESEM, and TEM analyses. The results showed that the composite with 150 mg of g-C₃N₄ nanoparticles had a good specific capacitance and enhanced electrochemical performance. The study concludes that the Co₃O₄-g-C₃N₄ composite electrode is a viable material for energy storage applications.