Double layer structure at the mercury/methanol solution interface

Abstract

Differential capacity against electrode potential data are presented for the mercury/methanol interface for a variety of salts at 25 °C and for NaClO4 solutions as a function of temperature. Ionic specific adsorption from solutions of KF, NaClO4, and LiBF4 was shown to be absent on the basis of the usual criteria. The dielectric properties of the inner layer are discussed on the basis of the three-state model for solvent structure from which it is deduced that the majority of solvent molecules are adsorbed at mercury with their dipole vectors parallel to the interface. The deep minimum in inner layer differential capacity, which occurs at the same electrode charge density independent of the nature of the salt (−0.05 C m−2), corresponds to conditions for which the surface concentrations of the minority components, dipoles oriented with the field or against it, are equal. The experimental temperature coefficient of the inner layer capacity is a maximum at this charge density in agreement with the predictions of the three-state model.