<p>This work presents a one-step pyrolysis approach to synthesize graphitic carbon nitride nanosheets grafted with copper nickel oxide (GCN-NS-g-CuNiO₂) at various temperatures. Structural and elemental analyses were conducted by X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX), confirming the successful formation of crystalline CuNiO₂ integrated with g-C₃N₄ nanosheets. The morphological features and porosity of the composites were examined using field-emission scanning electron microscopy (FESEM), revealing a porous nanosheet structure favorable for electrochemical applications. Among the prepared samples, the electrode fabricated at 350&#xa0;°C (GCN-NS-g-CuNiO₂@350) exhibited the best electrochemical performance, delivering a higher specific capacitance of 288.33 F g⁻¹ at 0.5 A g⁻¹ in 6.0&#xa0;M KOH electrolyte, attributed to efficient Faradaic redox activity. In addition, an asymmetric supercapacitor (ASC) device based on GCN-NS-g- CuNiO₂@350 and activated carbon (AC) was constructed, achieving a specific capacitance of 45.2 F g⁻¹ at 0.5 A g⁻¹ with good cyclability, retaining ~ 95% of its initial capacitance after 2000 charge–discharge cycles. These findings highlight the potential of GCN-NS-g-CuNiO₂ composites as advanced materials for high-performance supercapacitors.</p>