Study on Preparation and Electrochemical Properties of Biomass-Derived Spherical Activated Carbon

Abstract

Spherical activated carbon (SPs) with hierarchical porous structure was prepared via a simple solvent evaporation method followed by an activation process using leonardite humic acid (LHA) as carbon source. The surface morphologies and pore parameters of the as-prepared SPs were analyzed by scanning electron microscope (SEM) and N₂ physical adsorption-desorption instrument. The electrochemical performance of supercapacitors tested by galvanostatic charge-discharge (GCD), cyclic voltammograms (CV) and electrochemical impedance spectroscopy (EIS) are conducted in both aqueous and organic electrolyte. The SPs with high specific surface area (2034 m² g^-1) and pore volume (1.24 cm³ g^-1) exhibit a superior higher specific capacitance of 319 F g^-1 at a current density of 0.05 A g^-1 in aqueous electrolyte compared with powdered activated carbon (SP1). In addition, SPs1 also exhibit a high initial specific capacitance of 154 F·g^-1 at 0.05 A·g^-1 and a higher capacitance retention of 96.4% than the bulked sample started from the same raw materials in organic electrolyte. These results suggest that the LHA-based spherical activated carbon should be a competitive and promising supercapacitor electrode material.