Fabrication of a hybrid reduced graphene oxide functionalized ZnO/ZnCo2O4 nanocomposite for electrochemical energy storage

Abstract

Recent advancements have positioned supercapacitors as one of the most promising energy storage technologies in modern innovation. A primary focus of research to enhance their performance lies in developing and characterizing advanced electrode materials with high conductivity and energy density. In this study, reduced graphene oxide based hybrid ZnO/ZnCo₂O₄ nanocomposite was synthesized via a simple reflux method. The successful formation of the nanocomposite was confirmed through various characterization techniques, including X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), Ultraviolet–visible (UV–Vis), Scanning Electron Spectroscopy (SEM) and Transmission Electron Spectroscopy (TEM) studies. The surface area of the nanocomposite was analyzed by Brunauer–Emmett–Teller (BET) study. The electrochemical properties of the synthesized nanocomposite were assessed using cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) tests in a two-electrode configuration with 1 M KOH as the electrolyte. The results revealed a high specific capacitance of 646 F/g at 1 A/g and excellent cyclic stability, retaining 84.8 % of its initial capacitance even after 4000 cycles. The device also demonstrated impressive specific energy and power, achieving 50.28 Wh/kg and 2999 W/kg respectively. Additionally, charge storage mechanisms were investigated using the Trasatti plot, which indicated a balanced contribution from electric double-layer capacitance (EDLC, 51.45 %) and pseudo capacitance (CPC, 48.55 %). These results highlight the ZnO/ZnCo₂O₄-rGO nanocomposite as a highly promising material for energy storage applications, offering optimized total capacitance through the combined contributions of EDLC and pseudo capacitance.