Urchin-like Hierarchical Cu-NiCo ₂ O ₄ /g-C ₃ N ₄ Nanostructures as Advanced Electrode Materials for High-Performance Supercapacitors

Supercapacitors (SCs) are highly efficient for energy storage, offering fast charging and discharging and exceptional cycle stability. NiCo2O4 oxides are highly regarded as potential electrode materials due to their unique characteristics. The Cu-NiCo2O4/g-C3N4 material was prepared using a hydrothermal process. The introduction of Cu ions into NiCo2O4 improved electrical conductivity and provided redox-active sites, while g-C3N4 provided a high-surface-area, conductive substrate for efficient electron and ion transport. The composites were analyzed using X-ray diffraction (XRD), Raman spectroscopy, nitrogen adsorption isotherms, field-emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS). Galvanostatic charge–discharge (GCD) studies showed that the maximum specific capacitance of Cu-NiCo2O4/g-C3N4 was 743.3 F/g at 1 A/g. An asymmetric supercapacitor (ASC) was built using Cu-NiCo2O4/g-C3N4//AC composites, with activated carbon (AC) as both positive and negative electrodes. It achieved a maximum energy density (ED) of 25.46 Wh/kg, a power density (PD) of 749.7 W/kg, and 95% capacitance retention after 5000 cycles. The Cu-NiCo2O4/g-C3N4 composite exhibits exceptional electrochemical performance, driven by the combined effects of Cu doping and g-C3N4 incorporation, making it a suitable choice for future energy storage devices.