Ml. Foresti et al., ADSORPTION OF N-HEXANOL ON AG(100) AND AG(110) FROM AQUEOUS 0.05 M KCLO4, Journal of electroanalytical chemistry [1992], 376(1-2), 1994, pp. 85-95
The adsorption behaviour of n-hexanol (NHEX) on a Ag(100) single-cryst
al electrode surface from aqueous 0.05 M KClO4 was investigated on the
basis of capacitive charge measurements carried out by a computerized
chronocoulometric apparatus. The adsorption data were analysed thermo
dynamically and the resulting parameters were compared with a molecula
r model (R. Guidelli and M.L. Foresti, J. Electroanal. Chem., 197 (198
6) 103), leading to the conclusion that the NHEX molecules are adsorbe
d in a flat orientation just as on mercury and on Ag(111). The standar
d Gibbs energy of adsorption, Delta G degrees(ads) on Ag(100) was dete
rmined as a function of the electrode potential and of the capacitive
charge density. The differential capacity at the interface between Ag(
110) and aqueous 0.05 M KClO4 was found to be only very slightly depre
ssed upon saturating the solution with NHEX: this points to a vanishin
gly small adsorptivity of NHEX on this face. The adsorption parameters
for NHEX adsorption on Ag(100) are compared with those on Ag(111); in
particular Delta G degrees(ads) at the potential of maximum adsorptio
n equals -17.7 kJ mol(-1) on Ag(100) and -18.4 kJ mol(-1) on Ag(111).
The scale of hydrophilicity for sp metals, Ag(100) and Ag(111), based
on the corresponding Delta G degrees(ads) values for NHEX adsorption i
s in fairly good agreement with that based on Trasatti's interfacial p
arameter Delta X (S. Trasatti, J. Electroanal. Chem., 329 (1992) 237),
with the hydrophilicity increasing in the order Hg << Ag(111) < Ag(10
0) < Ag(110); however, the Delta G degrees(ads) Value for Ag(110) is a
nomalously low.