In this study, cobalt oxide is investigated as a binder-free electrode material for supercapacitor applications. Cobalt oxide nanostructures were directly grown on nickel foam using a simple hydrothermal method and the effect of hydrothermal reaction time on the structure and electrochemical performance was systematically examined. This electrode design eliminates inactive binders and improves electrical contact with the current collector. Structural and morphological analyses confirm the formation of phase-pure cobalt oxide with greater burdock-like nanostructure. Such features promote electrolyte penetration and facilitate rapid ion transport. The optimized electrode exhibits dominant pseudocapacitive behavior arising from reversible cobalt redox reactions and delivers a high specific capacitance of 1616.36 F g-1. The practical performance of the material was further demonstrated in a symmetric supercapacitor device. The device shows excellent cycling stability, retaining 93.84 % of its initial capacitance after 5000 charge-discharge cycles. The enhanced performance is attributed to the binder-free architecture, flower-like morphology and the multivalent redox activity of cobalt oxide. These results highlight the potential of hydrothermally synthesized cobalt oxide electrodes for high-performance supercapacitor applications.

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