Abstract
The micropores and surface oxygen functional groups of KOH-activated carbons were respectively extended and desorbed by the gasification of CO 2 during the activation process of chars derived from pistachio shells. These activated carbons (ACs) were found to exhibit ideal capacitive performances (i.e., a rectangular shape of CVs at a wide range of scan rates, high power property, and excellent reversibility) in aqueous electrolytes for electric double-layer capacitors. Although the specific capacitance of these ACs measured at a low scan rate (25 mV s -1 ) is decreased with reducing the density of surface functional groups, the ideal capacitive characteristics can be maintained at a much higher scan rate (300 mV s -1 ) when the CO 2 gasification time is equal to or longer than 30 min because of the relatively high proportion of mesopores. © 2006 Elsevier Ltd. All rights reserved.