Binder-Free Gr/CuO/Ni(OH)2 Hybrid Electrode for Enhanced Supercapacitor Performance via Two-Step Electrochemical Synthesis

Abstract

Hybrid energy storage systems that combine capacitive and faradaic materials offer a promising way to bridge the performance gap between batteries and supercapacitors. In this work, CuO/Ni(OH)₂ nanocomposites were produced on graphite electrode using a two-step electrochemical deposition process that did not require the use of binders. Structural and morphological characterisations using interferometric profilometry, scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and X-ray Diffraction (XRD) confirmed the successful formation of the hybrid architecture. Electrochemical tests in 4 M KOH revealed that the Gr/CuO/Ni(OH)₂ electrode delivered a high areal specific capacitance of 488.2 mF cm⁻² at 0.2 mA cm⁻², excellent stability over 6000 cycles with a capacitance retention of 88.75% and superior performance compared to single-component electrodes. The hybrid device Gr/CuO/Ni(OH)₂//AC exhibited an energy density of 14.97 μWh cm⁻² at a power density of 0.179 mW cm⁻². Two hybrid supercapacitors connected in series successfully illuminated a red and a yellow LED for several minutes. These results confirm the strong synergistic effect and high application potential of the Gr/CuO/Ni(OH)₂ nanocomposite for advanced supercapacitor systems.