Electrical double layer capacitors with activated sucrose-derived carbon electrodes

Electrical double layer capacitors (EDLCs) with activated sucrose-derived carbons (ASCs) as electrodes are reported. The carbons were prepared by the pyrolysis of sucrose followed by the activation with CO2 gas for 1-5 h at 900 degrees C to tune the pore size distribution and the specific surface area (SSA). The porosity of the AScs has been characterized using N-2 and CO2 adsorption measurements. The activation increased the SSA from similar to 200 to 3000 m(2) g(-1) and produced pores mostly in the 0.4-2 nm range. The pyrolysis of sucrose without CO2 activation produces a carbon with specific capacitance as low as 4 F g(-1), whereas selected ASCs exhibit specific capacitance in excess of 160 F g(-1) and excellent frequency response in a two-electrode EDLC cell with 1 M H2SO4 electrolyte. The activation time of 4 h resulted in the most promising electrochemical performance. Excellent ASC stability was confirmed by extensive electrochemical characterization after 10,000 charge-discharge cycles. (C) 2011 Elsevier Ltd. All rights reserved.