Green synthesis of ZnO–rGO nanocomposites for symmetrical supercapacitor electrode

This study shows a green reduction approach for the reduction of graphene oxide (GO) into reduced graphene oxide (rGO) nanosheets using Nicotiana tabacum (tobacco) leaf extract in a wet chemical process at low temperature (70°C). A similar process has been employed to produce ZnO–rGO nanocomposites (NCs). As-synthesized rGO and ZnO–rGO NCs have been investigated with X-ray diffraction, Raman spectroscopy, Fourier-transform infrared spectroscopy, UV–visible spectroscopy, and scanning electron microscopy–energy-dispersive X-ray analysis (SEM–EDX). Raman and EDX tests confirm a considerable reduction of oxygen-containing functional groups from GO in the production of rGO. Furthermore, the produced rGO and ZnO–rGO NCs have been tested as electrode materials for symmetrical supercapacitors (SSCs). The electrochemical performance has been found and obtained high specific capacitance of ∼207.5 F/g for rGO and 340 F/g for ZnO–rGO NCs at a current density of 2 A/g, respectively. The energy densities of rGO and ZnO–rGO NCs are calculated to be ∼18.44 and 30.22 Wh/kg, and power densities ∼1508.72 and 1942.71 W/kg, respectively. Cycling studies at 100 mV/s revealed exceptional retention, with 93.2% capacitance remaining after 2000 cycles for NCs. Thus, the eco-friendly method produced rGO and ZnO–rGO NCs successfully with excellent SSCs electrochemical performance.