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Stoeckli, Fritz

Nom
Stoeckli, Fritz
Affiliation principale
Fonction
Professeur.e émérite
Email
fritz.stoeckli@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/471

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  • Publication
    Accès libre
    Correlation between capacitances of porous carbons in acidic and aprotic EDLC electrolytes
    (2007)
    Centeno, Teresa A.
    ;
    Hahn, M.
    ;
    Fernández, J. A.
    ;
    Kötz, R.
    ;
    Stoeckli, Fritz 
    A study based on a total of 41 nanoporous carbons shows that there exists a good correlation between the limiting gravimetric capacitances Co at low current densities j (1 mA cm −2 ) measured in aprotic (1 M (C2H5)4NBF4 in acetonitrile) and in acidic (2 M aqueous H2SO4) electrolytes. The comparison of the surface-related capacitances (F m −2 ) of well characterized samples with the amount of thermodesorbed CO suggests a strong contribution of CO generating surface groups to charge storage in the acidic electrolyte, but a negligible contribution in the aprotic medium. It also appears that the decrease of the capacitance with current density is similar in both electrolytes. This confirms that the average micropore width and the CO2 generating surface groups are the main factors which limit the ionic mobility in both electrolytes.
  • Publication
    Accès libre
    The role of textural characteristics and oxygen-containing surface groups in the supercapacitor performances of activated carbons
    (2006)
    Centeno, Teresa A.
    ;
    Stoeckli, Fritz 
    It is suggested that the specific capacitance C0 of activated carbons at low current densities (d ~ 1 mA cm−2) consists, to a good first approximation, of two contributions. For the H2SO4 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 CO2-generating surface groups and on 1/L0, the inverse of the average micropore width.