Biowaste Derived Highly Porous Carbon for Energy Storage

Abstract

The demand for activated carbon (AC) is incessantly growing with population, due to its widespread applications in wastewater treatment, air purification, hydrogen storage, gas separation, and energy storage devices, but the complicated fabrication procedures, necessity of sophisticated instruments, and requirement of expensive precursors restrict its use. In this article, extremely porous activated carbon has been prepared from biowaste sweet lime peels (Citrus limetta). KOH solution was used as an activator because of its low activation temperature and high product yield. Carbonization was performed at 500 ℃. The structural and morphological properties of as prepared porous carbon were investigated by X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM). Electrochemical characterizations such as cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) were carried out at different scan rates and current densities in an aqueous electrolyte (1 M H2SO4). The GCD for activated carbon electrodes resulted in superior electrochemical performance with a high specific capacitance of about 243 F/g at 1 A/g. The activated carbon also showed excellent cyclic stability over 5000 charge–discharge cycles without any reduction in its initial capacitance. This shows the excellent performance of sweet lime peels derived AC as a stable and inexpensive material for energy storage applications.