Green Sol–gel Synthesis of Cu/Co₃O₄ Nanocomposite Using Curcuma Longa Leaf Extract for High-performance Supercapacitor Electrodes
J. Environ. Nanotechnol., Volume 15, No 1 (March 2026) pp. 543-554
Abstract
Cobalt oxide (Co₃O₄)–based nanocomposites have attracted considerable attention as promising electrode materials for high-performance supercapacitors due to their rich redox activity and structural stability. In this work, a Cu/Co₃O₄ nanocomposite was synthesized via a green sol–gel route using Curcuma longa leaf extract as a natural reducing and stabilizing agent. UV–Vis spectroscopy revealed characteristic absorption bands at 333.1 and 373.3 nm, while XRD and SEM analyses confirmed the formation of crystalline Cu/Co₃O₄ nanorods with uniform morphology. The electrochemical behavior of the fabricated Cu/Co₃O₄ electrode was evaluated in 1 M KOH using cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy. The electrode exhibited dominant pseudocapacitive behavior with a high specific capacitance of 345 F g⁻¹ at 1 A g⁻¹, excellent cycling stability with 95.3% capacitance retention after 5000 cycles, and a coulombic efficiency of ~99%. The low charge-transfer resistance and favorable ion-diffusion characteristics further confirm the efficient charge-storage kinetics of the nanocomposite. These results demonstrate that the green-synthesized Cu/Co₃O₄ nanocomposite is a viable and sustainable electrode material for advanced electrochemical energy-storage applications.
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