Investigation of cyclic voltammetry, impedance spectroscopy and electrical properties of thermally exfoliated biomass-synthesized graphene

In this paper we have reported the synthesis of graphene by a novel and facile thermal exfoliation process of Allium cepa (Onion) and was characterized by scanning electron microscopy, atomic force microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy to investigate the morphological and structural properties and chemical networks present on it. The AFM and SEM images revealed the formation of thin strip-like layered structure of graphene with the thickness of 1.1 nm. The electrochemical properties of graphene were characterized by cyclic voltammeter, impedance spectroscopy, Tafel plot, Nyquist plot, Bode plot, and voltage-dependent impedance using 0.5 M H2SO4 electrolyte as an illustrative standard material. The cyclic voltammetric curve of graphene electrodes determined a quasi-reversible electrochemical behavior under linear diffusion control square shape at higher process temperature. The ratio of atomic % C-to-O varied from 7.57 to 24.04 indicating a decrease in the oxygen content for the graphene processed at higher temperature. The areal capacitance and voltage-dependent impedance varied from 8.59 x 10(- 5) to 18.8 x 10(- 5) F/cm(2) and 15.79 to 7.7 Ohm, respectively, with the process temperature varying from 600 to 1000 degrees C. The corrosion potential (E-corr) and corrosion current density (I-corr) values are - 0.12 V and - 9.1A/cm(2), respectively, for the graphene processed at 1000 degrees C.