Micro–mesoporous carbons from rice husk as active materials for supercapacitors

Activated carbons were prepared from rice husk carbonized in the fluidized catalysts bed reactor. Using the different activating agents, samples with BET surface area in the range from 540 to 3060 m 2 /g were achieved. Using sodium or potassium carbonates results in the BET surface area up to 1400 m 2 /g. Hydroxides of sodium or potassium yield the samples with the higher BET surface area (up to 3060 m 2 /g). Textural peculiarities of the carbons were studied by the adsorption of nitrogen at 77 K and of carbon dioxide at 273 K. As active materials for supercapacitors, the porous carbon samples were examined by cyclic voltammetry and chronopotentiometry in galvanostatic mode in 1 M H 2 SO 4 as the electrolyte using home-made three-electrode electrochemical glass cell. Gravimetric capacitance of the carbons is linearly proportional to the BET surface area and reaches 230 and 196 F/g at discharge current density of 0.2 and 1 A/g, respectively, for the samples with the highest surface area.