Rice Husk Derived Micro-Mesoporous Carbon Materials as Active Components of Supercapacitor Electrodes

Abstract

Activated carbon materials (CM) were prepared from rice husk carbonized in the fluidized catalysts bed reactor. Textural characteristics of CM were studied by the adsorption of nitrogen at 77 K. Variation of synthesis conditions (conditions of carbonization and following activation) allowed to obtain materials with specific BET surface area from 440 to 2290 m²/g. Utilization of sodium or potassium carbonates results in the BET surface area up to 1200 m²/g. Activation by hydroxides of sodium or potassium yields the samples with the more developed surface up to 2290 m²/g. Electrochemical properties and capacitive characteristics were examined by cyclic voltammetry and chronopotentiometry in galvanostatic mode in aqueous electrolyte 1 M H₂SO₄ and ionic liquid BMIMBF₄. It was shown, that at low charge/discharge rate (0.2 А/g) gravimetric capacitance depends linearly on specific surface of CM and does not depend on electrolyte nature. Insignificant (in the case of 1 М H₂SO₄) and significant (in the case of ionic liquid) decrease of specific capacitance is observed at high rates of charge/discharge (2 А/g), which is explained by influence of porous structure.