Comparison of capacitive behavior of activated carbons with different pore structures in aqueous and nonaqueous systems

Abstract

The pore structures of two activated carbons from sawdust with KOH activation and coconut-shell with steam activation for supercapacitor were analyzed by N₂ adsorption method. The electrochemical properties of both activated carbons in 6 mol/L KOH solution and 1 mol/L Et₄NPF₄/PC were compared, and the effect of pore structure on the capacitance was investigated by cyclic voltammetry, AC impedance and charge-discharge measurements. The results indicate that the capacitance mainly depends on effective surface area, but the power property mainly depends on mesoporosity. At low specific current (1 A/g), the maximum specific capacitances of 276.3 F/g in aqueous system and 123.9 F/g in nonaqueous system can be obtained from sawdust activated carbon with a larger surface area of 1 808 m²/g, but at a high specific current, the specific capacitance of coconut-shell activated carbon with a higher mesoporosity of 75.1% is more excellent. Activated carbon by KOH activation is fitter for aqueous system and that by steam activation is fitter for nonaqueous system.

Keywords

activated carbon / supercapacitor / aqueous system / nonaqueous system / capacitance