Copper (II) anchored on guanidine-functionalized graphene oxide as a high-performance supercapacitor electrode: An experimental and theoretical investigation

Abstract

This study investigates a low-cost and effective supercapacitor (SC) electrode material that represents an important step toward sustainable development. For this purpose, copper (II) anchored on guanidine-functionalized graphene oxide (GGO/Cu) was synthesized via a facile two-step route. Various analytical techniques, such as Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and elemental mapping, were utilized for phase and morphology investigation of the GGO/Cu. The electrochemical performance was assessed through cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge/discharge (GCD) in the 6 M KOH electrolyte. The GGO/Cu electrode demonstrated a high specific capacitance of 1224 F g⁻¹ in the potential window of 0 to 0.45 V at the current density of 2 A g⁻¹. The as-prepared electrode exhibited excellent cyclic stability and good capacitance retention of 68 % after 5500 cycles at the high current density of 20 A g⁻¹. Furthermore, for theoretical studies of GGO/Cu electrode, density functional theory (DFT) calculations were employed and the results suggested the improvement of the quantum capacitance (C_Q) and confirmed the experimental findings.