Sweet‐Lime‐Peels‐Derived Activated‐Carbon‐Based Electrode for Highly Efficient Supercapacitor and Flow‐Through Water Desalination

Abstract

AbstractIn the present work, highly porous activated carbon with an excellent surface area has been successfully synthesized from the agricultural waste product; sweet lime peels (Citrus limetta) using a facile chemical approach. The structural and morphological properties of sweet lime peels derived activated carbon (SLP‐AC) were studied using X‐ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and X‐ray photoelectron spectroscopy (XPS). Brunauer‐Emmett‐Teller (BET) surface area and pore structure were studied using nitrogen adsorption‐desorption isotherms. Electrochemical characterizations were performed in two and three electrode cell configurations using techniques like cyclic voltammetry (CV), Galvanostatic charge‐discharge (GCD) and electrochemical impedance spectroscopy (EIS) in aqueous (1 M H2SO4 and 1 M NaCl) and ionic liquid electrolytes (EMIMBF4). SLP‐AC based electrodes showed high electrochemical charge storage capacity of 421.67 F/g (at 1 A/g) along with outstanding cyclic stability up to 10000 GCD cycles. Fabricated supercapacitor device demonstrated high energy density of 45.53 Wh/kg in the ionic liquid electrolyte. SLP‐AC was also used to prepare the porous sponge electrodes to study their applicability in flow‐through electrode capacitive deionization (CDI), where it achieved the maximum electrosorption capacity of 22.8 mg/g. The electrosorption results fitted well with the Langmuir isotherm and the kinetics study indicates a pseudo‐first‐order kinetic model for the electrosorption of salt ions onto the electrodes surface. This confirms the outstanding performance of SLP‐AC as a highly stable and low‐cost electrode material for supercapacitors and water desalination applications.