Highly carbonized Prunus dulcis shell-derived activated carbon for high-performance supercapacitor applications

Recently, the supercapacitor has gained more consideration due to its speedy charging and discharging, high power density, and stability compared to the existing batteries. Activated carbon-based electrodes for the supercapacitor provide higher specific capacitance. In this research, activated carbon was obtained from Prunus dulcis (almond fruit) shell by carbonization using a muffle furnace. Carbonized Prunus dulcis fruit shells were chemically activated by potassium hydroxide (KOH). X-ray diffraction (XRD) patterns of KOH-activated carbon derived from Prunus dulcis shell evident that the activated carbon samples are amorphous. The scanning electron microscope (SEM) images of activated carbon derived from Prunus dulcis exhibited a 2D sheet-like morphology and a smooth surface. Energy-dispersive X-ray spectroscopy (EDX) detected oxygen, chloride, and potassium peaks with 85.2% carbon. The addition of KOH helped to increase the porosity of the fruit shells and enhanced the absorption of the electrolyte. The supercapacitor electrode was prepared by coating activated carbon on a graphite pencil lead. The performance of the electrode was evaluated using a 6 M KOH electrolyte at various current densities and scan rates. The prepared sample was electrochemically characterized by cyclic voltammetry, galvanostatic charge and discharge measurements, and electrochemical impedance spectroscopy. From the analysis, the suitability of the material as an electrode can be understood. The specific capacitance of the samples was measured as 434, 237, 105.9, and 50.5 F g−1 at 1, 2, 4, and 10 A g−1, respectively. The higher specific capacitance is ascribed to the high specific surface area, electrolyte, and pore volume. And also, at an energy density of 0.28 Wh g−1, the power density of 100 kW g−1 is obtained. The electrode has a series resistance of 10.51 Ω and a charge transfer resistance of 1.12 Ω.