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Université de Neuchâtel

Chars and Activated Carbons Prepared from Asturian Apple Pulp

Fernandez, Elena ; Centeno, Teresa A. ; Stoeckli, Fritz

In: Adsorption Science and Technology, 2001, vol. 19, no. 8, p. 645-653

Asturian apple pulp was carbonised under nitrogen at 400ºC and 750ºC and subsequently activated with CO2 at 750ºC. The resulting active carbon exhibited properties in line with those expected from precursors of vegetable origin, with the carbonisation stage appearing to have only a limited influence on the final porosity. In the case of carbonisation at 400ºC, the initial micropore...

Université de Neuchâtel

On the activation of Asturian anthracite following various pretreatments

Centeno, Teresa A. ; Stoeckli, Fritz

In: Carbon, 1994, vol. 32, no. 8, p. 1463-1467

An Asturian anthracite has been subjected to different pretreatments and subsequently activated by steam at 850°C to a total burn-off of 55 percent. The physical properties (micropore sizes and distributions, external surface areas, etc.) of the solids are compared with those of the carbon obtained by direct activation. Although the yield is generally low, it appears that better results are...

Université de Neuchâtel

The oxidation of an Asturian bituminous coal in air and its influence on subsequent activation by steam

Centeno, Teresa A. ; Stoeckli, Fritz

In: Carbon, 1996, vol. 33, no. 5, p. 581-586

It is shown that the oxidation of an Asturian bituminous coal by air, at 150 ° and 270 °C, has a considerable influence on the microporous structure of the carbon obtained by subsequent carbonization and steam activation to 50% burn-off. The direct activation of the coal leads to an open micropore system of 0.2 cm3/g, with an average pore size near 0.8 nm. On the other hand, much larger systems...

Université de Neuchâtel

Porous structure of polyarylamide-based activated carbon fibres

Stoeckli, Fritz ; Centeno, Teresa A. ; Fuertes, A. B. ; Muñiz, J.

In: Carbon, 1996, vol. 34, no. 10, p. 1201-1206

Activated carbons were prepared from two polyarylamide fibres (Kevlar and Nomex) by carbonization and subsequent steam activation to 25 and 50% burn-off. The porous structure of the carbons has been investigated by physical adsorption of CH2Cl2 and N2O at 293 K and immersion calorimetry into liquids of different molecular dimensions. The activated fibres have...

Université de Neuchâtel

On the characterization of microporous carbons by immersion calorimetry alone

Stoeckli, Fritz ; Centeno, Teresa A.

In: Carbon, 1997, vol. 35, no. 8, p. 1097-1100

Immersion calorimetry is a useful tool for the characterization of solid surfaces in general, but in the case of microporous solids it usually requires complementary information, obtained from an adsorption isotherm. This article demonstrates the possibilities and the limitations of this technique when used alone. It appears that the use of a standard value for the enthalpy immersion does not...

Université de Neuchâtel

Improvement of the structural and chemical properties of a commercial activated carbon for its application in electrochemical capacitors

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

In: Electrochimica Acta, 2008, vol. 53, no. 5, p. 2210-2216

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...

Université de Neuchâtel

EDLC performance of carbide-derived carbons in aprotic and acidic electrolytes

Fernández, J. A. ; Arulepp, M. ; Leis, J. ; Stoeckli, Fritz ; Centeno, Teresa A.

In: Electrochimica Acta, 2008, vol. 53, no. 24, p. 7111-7116

This study shows that carbide-derived carbons (CDCs) with average pore size distributions around 0.9–1 nm and effective surface areas of 1300–1400 m2 g−1 provide electrochemical double-layer capacitors with high performances in both aqueous (2M H2SO4) and aprotic (1M (C2H5)4NBF4 in acetonitrile)...

Université de Neuchâtel

Cherry stones as precursor of activated carbons for supercapacitors

Olivares-Marín, M. ; Fernández, J. A. ; Lázaro, M. J. ; Fernández-González, C. ; Macías-García, A. ; Gómez-Serrano, V. ; Stoeckli, Fritz ; Centeno, Teresa A.

In: Materials Chemistry and Physics, 2009, vol. 114, no. 1, p. 223-227

It is shown that cherry stones-wastes can be recycled as activated carbons for electrode material in supercapacitors. KOH-activation of this precursor at 800–900 °C is an efficient process to obtain carbons with large specific surface areas (1100–1300 m2 g−1), average pore sizes around 0.9–1.3 nm, which makes them accessible to electrolyte ions, and conductivities...

Université de Neuchâtel

Correlation between heats of immersion and limiting capacitances in porous carbons

Centeno, Teresa A. ; Fernández, J. A. ; Stoeckli, Fritz

In: Carbon, 2008, vol. 46, no. 7, p. 1025-1030

Based on more than 80 carbons, the paper shows that immersion calorimetry into benzene, water and carbon tetrachloride can be used to assess with a good accuracy the limiting capacitance Co at low current densities in both acidic (2 M H2SO4) and aprotic (1M tetraethyl ammonium tetrafluoroborate in acetonitrile) electrolytic solutions. The enthalpies of immersion...

Université de Neuchâtel

Applications of Immersion Calorimetry in Dubinin’s Theory and Electrochemistry

Stoeckli, Fritz ; Centeno, Teresa A.

In: Recent Advances in Adsorption Processes for Environmental Protection and Security, 2008, vol. 18, no. 2, p. 9-18

This study shows that immersion calorimetry is a useful technique which simplifies considerably the analysis of porosity and chemical nature of activated carbons. The characterization of activated carbons in the general theoretical framework of Dubinin's theory with its extensions to calorimetry and adsorption from solutions allows the identification of some key parameters for the performance of...