Wh. Mulder et Bs. Bharaj, ON THE EQUIVALENCE OF FREE (1) ENERGY AND PRESSURE PROFILE METHODS FOR DETERMINING THE MECHANICAL-PROPERTIES OF DOUBLE-LAYERS, Journal of electroanalytical chemistry [1992], 421(1-2), 1997, pp. 59-65
The thermodynamics of electrified interfaces (electrode\electrolyte an
d colloid systems) are re-examined, leading to a quantitative expressi
on for the lowering of interfacial tension (surface pressure) due to t
he adsorbed ions in terms of hydrostatic and electrostatic contributio
ns. Expressions are derived for the variation of these quantities acro
ss the double layer. It is shown that the classical expression for the
double layer free energy leads to an incorrect result when applied to
a double layer with a mobile layer of surface ions. Explicit results
are given for a simplified model for the diffuse ionic layer based on
a mean-field approximation (Gouy-Chapman theory).