Interfacial synergy in NiCo₂O₄@g-C₃N₄ heterostructures for advanced supercapacitors and selective organic pollutant degradation

The development of efficient electrode materials is an important research area in advanced energy-storage technologies. In this study, a NiCo₂O₄@g-C₃N₄ heterostructure was synthesized via a facile hydrothermal method and investigated as a bifunctional material for supercapacitor and photocatalytic applications. The structural, morphological, and chemical properties of the synthesized materials were analysed using various characterization techniques. Electrochemical studies revealed that the NiCo₂O₄@g-C₃N₄ hybrid electrode exhibited enhanced charge-storage performance, delivering a high specific capacitance of 1776.4 F g^-1 at 2.4 A g^-1 in 3 M KOH electrolyte. The fabricated asymmetric supercapacitor demonstrated good energy-storage capability, retaining 94.48% of its capacitance after 6500 charge-discharge cycles, and produced a stable voltage sufficient to illuminate a red LED. Furthermore, the NiCo₂O₄@g-C₃N₄ nanocomposite exhibited superior visible-light-driven photocatalytic activity, achieving 96.17% degradation of methylene blue (MB) and 96.19% degradation of crystal violet (CV) within 150 min. The enhanced bifunctional performance is attributed to the synergistic interaction between NiCo₂O₄ and g-C₃N₄, which facilitates charge transfer, promotes efficient charge separation, and improves photocatalytic activity. These findings demonstrate the potential of NiCo₂O₄@g-C₃N₄ as a promising material for multifunctional energy-storage and photocatalytic applications.