Abstract
Fir wood-derived carbons activated with steam, KOH, and KOH + CO 2 were found to exhibit the high-power, low ESR, and highly reversible characteristics between -0.1 and 0.9 V in aqueous electrolytes, which were demonstrated to be promising electrode materials for supercapacitors. The pore structure of these activated carbons was systematically characterized by the t-plot method based on N 2 adsorption isotherms. Activated carbons prepared through the above three activation methods under different conditions (i.e., the gasification time of CO 2 , KOH/char ratio, and activation time of steam) generally showed excellent capacitive performance in aqueous media, mainly attributed to the development of both micropores and mesopores (with the meso-pore volume ratio, V meso /V pore , ranging from 0.18 to 0.52). Scanning electron microscopic (SEM) photographs showed that the surface morphologies of honeycombed holes were found to depend on the activation methods. The average specific capacitance of the activated carbon with a combination of KOH etching and CO 2 gasification (with gasification time of 15 min) reached 197 F g -1 between -0.1 and 0.9 V in H 2 SO 4 . The capacitive characteristics of steam- and KOH-activated carbons in NaNO 3 and H 2 SO 4 could be roughly estimated from the pore structure and BET surface area although the correlation may be only applicable for the fir wood-derived activated carbons. © 2005 Elsevier B.V. All rights reserved.