Synthesis of reduced graphene oxide and Nickel oxide/reduced graphene oxide composite materials for supercapacitor applications and their computational investigations

Abstract

This study outlines the synthesis of reduced graphene oxide (rGO) and Nickel oxide/reduced graphene oxide (NiO/rGO) composite materials without the use of binders. The synthesis method involved microwave-assisted reduction using ascorbic acid (AA) and varying weight ratios of potassium hydroxide (KOH) to convert graphene oxide (GO) to rGO. The research investigates how adjusting the weight ratios of GO and KOH influences the electrical conductivity (EC) properties of the synthesized materials, particularly exploring the impact of KOH addition on the porosity growth in the rGO layers during fabrication. Various analytical techniques, including optical, vibrational, morphological, bonding, and network analysis, were employed to characterize the synthesized materials. The materials were evaluated as potential supercapacitor electrodes using electrochemical techniques such as cyclic voltammetry and A.C. impedance analysis, including Nyquist and Bode plots. The specific capacitance (CS) of rGO and NiO/rGO was determined to be 1400 Fg−1 at a scan rate of 0.005 Vs−1. The synthesis process avoided the use of hazardous reagents. Additionally, density functional theory (DFT) based computational analysis was conducted to support the experimental findings. The study documents the influence of incorporating NiO onto the surface of GO and rGO on the energy gap (Egap) and investigates the density of state (DOS) to understand the effect of MO-rGO interaction. Furthermore, frontier molecular orbital (FMO) contours were examined to analyze excitation qualities, and electron potential was visualized and mapped onto the electron density surface to gain insights into charge dispersion within the structures.