Enhanced Specific Capacitance in Supercapacitor Fabricated With NiO‐Decorated Copper Oxide Electrode

Nickel oxide nanoparticles were decorated on copper oxide (NO@SCO) using a hydrothermal method at 150 °C. This nano‐heterostructure was characterised using X‐ray diffraction, X‐ray photoelectron spectroscopy (XPS), energy‐dispersive X‐ray spectroscopy, field‐emission scanning electron microscopy and field‐emission transmission electron microscopy for its phase purity, elemental and morphological studies. More significantly, it is observed that monoclinic CuO nanorods (40–50 nm) have been decorated with cubic NiO nanoparticles (40 nm). The nanostructure exhibited a dandelion‐like morphology decorated with NiO nanoparticles. Further XPS analysis clearly shows the presence of Cu and Ni with valency states. Electrochemical tests conducted in a 5 M NaOH electrolyte revealed that the introduction of 1% NiO significantly improved the charge–discharge performance, exhibiting low internal resistance and well‐defined symmetric cyclic behaviour, which is crucial for redox reactions. Notably, prolonged cycling of 5300 GCD cycles for half‐cell demonstrated a mean specific capacitance of 87.78 F g −1 at 2 A g −1 with a standard deviation of 2.48 F g −1 , despite some fading observed in higher cycles. The construction of a full‐cell symmetric capacitor utilising 1% NiO‐decorated CuO in a CR 2032‐coin cell yielded 89.7% capacitance retention over 2000 cycles at 0.2 A g −1 and a high Coulombic efficiency of 92.5%. The specific capacitance averaged 11.44 F g −1 with a standard deviation of 0.49 F g −1 , highlighting the suitability of the material for long‐term energy storage of symmetric full‐cell capacitor. The capacitive behaviour was maintained, underscoring the potential of this heterostructure for pseudocapacitor applications.