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Abstract:
The electrochemical performance of cobalt-based supercapacitor electrodes is often limited by the relatively smooth surface of pristine nickel foam substrates. To overcome this limitation, a microstructurally engineered nickel foam scaffold was fabricated by introducing a porous nickel microparticle interlayer via screen printing. Cobalt nanostructures were hydrothermally grown on the modified substrate, forming a hierarchical electrode (Co@NF-M), which was systematically compared with electrodes prepared on commercial nickel foam (Co@NF). Structural and spectroscopic analyses supported the formation of predominantly crystalline spinel Co3O4, characterized by mixed Co2 + /Co3+ oxidation states. Morphological analysis further demonstrated a porous cobalt nanostructure anchored onto a roughened nickel scaffold, providing abundant active sites and facilitating electrolyte penetration and ion diffusion. Electrochemical impedance spectroscopy indicated a reduced charge-transfer resistance and improved electron transport compared to the conventional Co@NF electrode. As a result, the Co@NF-M electrode exhibited superior electrochemical performance, delivering specific capacitances of 1278, 1184, 1003, and 602 F g−1 at 0.5, 1, 5, and 10 A g−1, respectively. Furthermore, the symmetric Co@NF-M//Co@NF-M device retained 95% of its initial capacitance after 3000 cycles, demonstrating excellent cycling stability. The enhanced performance is attributed to the engineered nickel scaffold, which promotes more uniform cobalt growth and improves interfacial contact while facilitating electron and ion transport.

Keywords:
Cobalt oxide, Symmetric supercapacitor, Cycling stability, Tailored Nickel foam, Pseudocapacitor behavior