Stoeckli, Fritz

2008, Lota, G., Centeno, Teresa A., Frackowiak, E., Stoeckli, Fritz

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 m² g⁻¹ and 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 H₂SO₄ and 6M KOH) and around 150 F g⁻¹ in 1M (C₂H₅)₄NBF₄ 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 (C₂H₅)₄NBF₄/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 (H₂SO₄ and KOH).

2005, Centeno, Teresa A., Sevilla, M., Fuertes, A. B., Stoeckli, Fritz