Symmetric supercapacitor based on biosynthesized nanosheets of reduced graphene oxide (rGO): Characterization and electrochemical behavior

Abstract

Reduced graphene oxide (rGO) nanosheets (NS) were synthesized via a simple, rapid, eco-friendly and cost effective biosynthesis approach using Lonar lake isolated bacterium strain Bacillus cabrialesii RIRD-SK (MCC 4670). The biologically prepared rGO nanosheets were characterized via X-ray detection diffraction (XRD), Fourier transform infrared spectrum (FTIR), Raman spectroscopy, Field emission scanning electron microscopy (FE-SEM), Energy dispersive X-ray spectroscopy (EDX), and Brunauer-Emmett-Teller (BET) techniques, respectively. Electrochemical investigation was carried out using the cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS) tests. Most of the oxygen functional groups species in rGO were successfully eliminated resulting in little (0.39 Ω) charge transfer resistance (Rct). The rGO electrode exhibited 457 F/g specific capacitance at scan rate 5 mV s−1 in 1 M Na2SO4 aqueous electrolyte within the potential window of −1 to 0 V. It showed a superior electrochemical cycle stability of 96 % after 10,000 cyclic voltammetry cycles. The aqueous symmetric supercapacitor device was prepared in the configuration of rGO/Na2SO4/rGO. Device exhibited 165 F/g specific capacitance at scan rate 5 mV s−1 with cyclic retention of 94 % for 10,000 cyclic voltammetry cycles.