The study of 28 porous carbons shows that the specific capacitance in the electrolyte (C(2)H(5))(4)NBF(4)/acetonitrile is relatively constant between 0.7 and 15 nm (0.094 ± 0.011 F m(-2)). The increase in pores below 1 nm and the lower values between 1 and 2 nm reported earlier are not observed in the present work.

Mesoporous carbons prepared by an inverse replica technique have been used as electrodes for electrochemical capacitors. Such well sized carbons were prepared from mesostructured SBA-16 silica materials that served as templates whereas polyfurfuryl alcohol was the carbon precursor. Two highly mesoporous carbons characterized by 3 and 8 nm average pore diameter were tested in various electrolytic solutions (acidic, alkaline and aprotic).It can be concluded that templated mesoporous carbons with tailored pore size distribution are very promising materials to be used as electrodes in supercapacitors.The design of their pore size allows suiting the dimensions of electrolyte ions and efficient charging of the electrical double layer is achieved especially at high current load. Definitively better capacitance performance has been found for carbon with 3 nm pores range, however, cycling performance depends not only on the pore size.

The present paper shows that the performance of an inexpensive activated carbon used in electrochemical capacitors can be significantly enhanced by a simple treatment with KOH at 850• C. The changes in the specific surface area, as well as in the surface chemistry, lead to high capacitance values, which provide a noticeable energy density.The KOH-treatment of a commercial activated carbon leads to highly pure carbons with effective surface areas in the range of 1300-1500 m 2 g −1and gravimetric capacitances as high as three times that of the raw carbon. For re-activated carbons, one obtains at low current density (50 mA g −1 ) values of 200 F g −1 in aqueous electrolytes (1M H 2 SO 4 and 6M KOH) and around 150 F g −1 in 1M (C 2 H 5 ) 4 NBF 4 in acetonitrile. Furthermore, the resulting carbons present an enhanced and stable performance for high charge/discharge load in organic and aqueous media.This work confirms the possibilities offered by immersion calorimetry on its own for the prediction of the specific capacitance of carbons in (C 2 H 5 ) 4 NBF 4 /acetonitrile. On the other hand, it also shows the limitations of this technique to assess, with a good accuracy, the suitability of a carbon to be used as capacitor electrodes operating in aqueous electrolytes (H 2 SO 4 and KOH).

It is suggested that the specific capacitance C 0 of activated carbons at low current densities (d ∼ 1 mA cm −2 ) consists, to a good first approximation, of two contributions. For the H 2 SO 4 electrolyte they correspond to approximately 0.080 F m −2 from the total accessible surface area and an additional pseudo-capacitance of 63 F mmol −1 from the surface species generating CO in thermally programmed desorption (TPD). The new correlation proposed here is an alternative to Shi's earlier approach which considered contributions from the microporous and the external surface areas. Furthermore, it appears that the variation of the specific capacitance C at high current densities d (up to 100-150 mA cm −2 ) depends essentially on the CO 2 -generating surface groups and on 1/L 0 , the inverse of the average micropore width.

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