Green synthesis of ZnO/carbon (ZnO/C) as an electrode material for symmetric supercapacitor devices

Abstract With the eco friendly green chemistry technique in mind, sucrose has been used in this study as the capping agent to synthesize ZnO/C nanocomposite adapting sol-gel method. The presence of carbon in the prepared ZnO/C was confirmed through EDAX. Electrochemical investigations of ZnO/C electrode were carried out using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The ZnO/C electrode exhibits a maximum specific capacitance of 820 F g−1 at a constant specific current of 1 A g−1. The symmetric aqueous supercapacitor device exhibits the specific cell capacitance of 92 F g−1 at the specific current of 2.5 A g−1. The aqueous symmetric supercapacitor device achieved an energy density of 32.61 Wh kg−1 and the power density of approximately 1 kW kg−1 at a discharge current of 1.0 A g−1. It has been found that the cells have an excellent electrochemical reversibility (92% after 400 continuous cycles) and capacitive characteristics in 1 M Na2SO4 electrolyte.