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 °C to tune the pore size distribution and the specific surface area (SSA). The porosity of the ASCs has been characterized using N₂ and CO₂ adsorption measurements. The activation increased the SSA from ∼200 to 3000 m² 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.