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On the specific double-layer capacitance of activated carbons, in relation to their structural and chemical properties

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Abstract
Twelve well-characterized activated carbons with average micropore widths between 0.7 and 2 nm, total surface areas of 378–1270m2 g−1 and specific capacitances C up to 320 F g−1 have been investigated, using H2SO4 2M as electrolyte. Some of the carbons have also been oxidized with (NH4)2S2O8, which leads to specific oxygen contents between 0.4 and 7.1
molm−2 of carbon surface area. It appears that
Co, the limiting capacitance at a current density of 1mAcm−2 of electrode surface, does not depend significantly on the oxygen content. An empirical equation is proposed to describe the decrease of C with increasing current density d (1–70mAcm−2 of electrode surface), as a function of the oxygen content.
As suggested by different authors, Co can be expressed as a sum of contributions from the external surface area Se and the surface of the micropores Smi. A closer investigation shows that Co/Smi increases with the pore size and reaches values as high as 0.250–0.270 Fm−2 for supermicropores. It is suggested that the volume Wo of the electrolyte found between the surface layers in pores wider than 0.7–0.8 nm contributes to Co. However, this property is limited to microporosity, like the enthalpy of immersion of the carbons into benzene. The latter is also correlated to Co, which provides a useful means to identify potential supercapacitors.

Keywords: Electrochemical capacitor; Activated carbon; Microporosity; Surface area; Surface oxygen; Calorimetry

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Informasi Detail

Judul Seri

Journal of Power Sources

No. Panggil

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Penerbit

: Elsevier B.V. All rights reserved., 2005

Deskripsi Fisik

Journal of Power Sources 154 (2006) 314–320

Bahasa

English

ISBN/ISSN

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Klasifikasi

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Tipe Isi

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Tipe Media

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Tipe Pembawa

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Edisi

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Subjek

KIMIA

Info Detail Spesifik

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Pernyataan Tanggungjawab

yuli/agus

Versi lain/terkait

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