Green Synthesis of Nickel Cobaltite Using Moringa oleifera Plant Extract for Electrode Materials in Sustainable Supercapacitor Energy Storage

Abstract

The importance of energy storage techniques has recently increased owing to the emergence of renewable energy sources and their consequent non-dispatchability. The supercapacitor is one among several prominent energy storage systems. The electrode assembly and constituents used in the construction of supercapacitors play a significant role in increasing their effectiveness. Among the several methods for the fabrication of electrode materials for supercapacitors, green synthesis is a sustainable method owing to its advantages like its eco-friendly nature, low cost, and ease of fabrication. In this study, a method was proposed to fabricate a nickel cobaltite (NiCo₂O₄) nanomaterial for the construction of supercapacitor electrodes using green synthesis to take advantage of NiCo₂O₄. Extracts of Moringa oleifera (drumstick) leaves were used to synthesize nanoparticles. Scanning electron microscopy with energy-dispersive x-ray spectroscopy and powder x-ray diffraction were used to characterize the NiCo₂O₄ biosynthesized nanoparticles. Important investigation techniques viz. cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy were used to investigate the electrochemical properties of the prepared nanomaterial. The fabricated nanomaterial displayed reasonably good specific capacitance values at different current densities. Furthermore, a supercapacitor device constructed using the synthesized nanomaterials and activated carbon showed an enhanced energy density of 19.8 Wh/kg at a power density of 748.81 W/kg with a good retention capacity of approximately 85% after 8000 cycles at a current density of 5 A/g. Green synthesis, with its inherent advantages over chemical methods, is expected to be a promising method for the fabrication of electrode materials for supercapacitors for acceptable energy storage characteristics in the future.