X-ray scattering and adsorption studies of thermally oxidized glassy carbon

The thermal oxidation of glassy carbon (GC) was studied in order to explore its potential as a porous electrode material for electrochemical double la yer capacitors (EDC). Thin GC sheet samples of 55 mu m thickness were activ ated by thermal oxidation to provide an active film with open pores on top of non-activated bulk material with closed pores. Nitrogen gas adsorption, electrochemical impedance spectroscopy and small angle X-ray scattering wer e applied to characterize the activated GC. The growth of the active film f ollows a square-root growth law with respect to activation time. It was fou nd that the internal volumetric surface area decreases upon activation, whe reas the volumetric electrochemical double layer capacitance increases. It was shown that this effect is correlated with the opening, the growth and t he coalescence of the pores. (C) 1999 Published by Elsevier Science B.V. Al l rights reserved.