Cresol-formaldehyde based carbon aerogel as electrode material for electrochemical capacitor

Carbon aerogels have been prepared through a polycondensation of cresol (Cm) with formaldehyde (F) and an ambient pressure drying followed by carbonization at 900 C-o. Modification of the porous structures of the carbon aerogel can be achieved by CO2 activation at various temperatures (800, 850, 900 C-o) for 1--3 h. This process could be considered as an alternative economic route to the classic RF gels synthesis. The obtained carbon aerogels have been attempted as electrode materials in electric double-layer capacitors. The relevant electrochemical behaviors were characterized by constant current charge-discharge experiments, cyclic voltammetry and electrochemical impedance spectroscopy in an electrolyte of 30% KOH aqueous solution. The results indicate that a mass specific capacitance of up to 78 F g(--1) for the non-activated aerogel can be obtained at current density 1 mA cm(--2). CO2 activation can effectively improve the specific capacitance of the carbon aerogel. After CO2 activation performed at 900 C-o for 2 h, the specific capacitance increases to 146 F g(--1) at the same current. Only a slight decrease in capacitance, from 146 to 131 F g(--1), was observed when the current density increases from 1 to 20 mA cm(--2), indicating a stable electrochemical property of carbon aerogel electrodes in 30% KOH aqueous electrolyte with various currents. (C) 2006 Elsevier B.V. All rights reserved.