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Highly porous activated glassy carbon film sandwich structure for electrochemical energy storage in ultracapacitor applications: Study of the porous film structure and gradient

Published online by Cambridge University Press:  31 January 2011

Artur Braun ,
Soenke Seifert  and
Jan Ilavsky
Artur Braun*
Affiliation:
Empa, Swiss Federal Laboratories for Materials Testing and Research, Laboratory for High Performance Ceramics, CH-8600 Dübendorf, Switzerland; Department of Chemical and Materials Engineering, University of Kentucky, Lexington, Kentucky 40506; and General Energy Research Department, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
Jan Ilavsky
Affiliation:
Argonne National Laboratory, Advanced Photon Source, Argonne, Illinois 60439
*
a)Address all correspondence to this author. e-mail: artur.braun@alumni.ethz.ch
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Abstract

Glassy carbon plates were thermochemically gas phase oxidized to obtain monolithic sandwichlike electrode assemblies with high surface area porous films for electrochemical energy storage applications. Film thicknesses were varied by variation of oxidation parameters time, temperature, and oxygen concentration and measured with electron microscopy. The mass density of the porous carbon film material was estimated by fitting a geometrical model to experimental gravimetric data. Optical Raman spectroscopy line scans suggest that the porosity has a gradient between the surface and the film/bulk interface, which is supported by pore-size distribution data obtained from small-angle x-ray scattering (SAXS) on slightly oxidized and fully oxidized samples. Detailed inspection of the power law behavior of SAXS data suggests that the internal surface area of well-oxidized glassy carbon (GC) is compact and extends over the entire probed volume and thus has optimal pore connectivity. This effect goes along with pore enlargement and a relative decrease of internal surface area per volume. Slightly oxidized carbon has no pore space with a compact, high connectivity internal surface area. The corresponding SAXS power law and the x-ray density suggest that this high volumetric surface area must be interpreted as a result of surface roughness, rather than true geometric or volumetric surface area. In consequence, is this surface area of limited use for electrochemical energy storage?

Keywords

PorosityOxidationEnergy storage
Type
Articles
Information
Journal of Materials Research , Volume 25 , Issue 8: Materials for Electrical Energy Storage , August 2010 , pp. 1532 - 1540
Copyright
Copyright © Materials Research Society 2010

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