Synthesis and Characterization of Electrochemically Reduced Graphene Oxide for Applications in Supercapacitors

Abstract

Graphene oxide (GO) was prepared from graphite by the modified Hummers’ method using strong oxidizing agents which was reduced removing its oxygen-containing functional groups. sp² carbon domains in GO material do not allow for electron transferring due to tight geometry and higher electronegativity of sp² orbitals than sp³ carbon centers. Successful synthesis of GO from graphite powder was confirmed by X-ray diffraction (XRD) technique showing a diffraction peak 2θ = ~9.8°. Further, GO reduction procedures were performed through electrochemical (three-electrode cell, 1 M KOH, potential range from 0 to -1.2 V) and chemical (1 M ascorbic asid, 60 °C, stirring) methods. Morphological (scanning electron microscopy (SEM) and transmission electron microscopy (TEM)), structural (X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy) and thermal (thermogravimetric analysis (TGA)) analyses confirmed the removal of oxygen-containing groups, indicating conversion from GO to reduced GO (rGO). The electrochemical characteristics (CV, GCD, EIS) were investigated in a symmetric two-electrode Swagelok-type cell using 1 M NaNO₃. Based on the obtained results, the most promising material was electrochemically reduced graphene oxide (E-RGO), where the capacitance increased from ~54 F·g^-1 at 0.7 V to ~67 F·g^-1 at 1.5 V at a specific current density of 200 mA·g^-1 in a 1 M NaNO₃ electrolyte. The specific capacitance of the E-RGO electrodes is 13.7% higher than that of chemically reduced graphene oxide (C-RGO), and these results demonstrate the effectiveness of electrochemically reduced graphene oxide, further demonstrating its potential applications in supercapacitors.