Synthesis of large surface area carbon xerogels for electrochemical double layer capacitors

Abstract

A resorcinol formaldehyde (R-F) condensation reaction catalyzed by acetic acid (C) is employed to prepare carbon xerogels for electrochemical double layer capacitors. The samples are fabricated with an R:F ratio of 1:2 and R:C ratio of 10:1, followed by solvent exchange, pyrolysis, and carbon dioxide activation. The solvent exchange allows negligible structure contraction upon drying, and after pyrolysis and carbon dioxide treatment, we are able to produce porous carbons with a surface area of 3419 m(2) g(-1). Image from scanning electron microscope reveals an interconnected foam-like structure and BET confirms the presence of excessive micro- and mesopores. Electrochemical analysis including cyclic voltammetry (CV), current reversal chronopotentiometry (CRC), and impedance spectroscopy are conducted using a titanium cavity electrode so relevant capacitive characteristics and kinetic parameters could be determined. Both CV and CRC results indicate specific capacitances and life time behaviors that are comparable or even better than those of Black Pearl 2000. For example, the specific capacitance is 324.8 F g(-1) in 0.5 M H2SO4 aqueous solution at +/- 1 A g(-1) for potential window of 0-1 V. In contrast, sample without carbon dioxide activation displays a similar morphology but its surface area and specific capacitance are reduced considerably to 449 m(2) g(-1) and 34.7 F g(-1), respectively. (C) 2012 Elsevier B.V. All rights reserved.