Abstract
Charge transfer between an electrode and the electrolyte proceeds by electron tunnelling between the electrode metal and a suitable electron acceptor or donor on the solution side of the electrode/electrolyte interface across very small distances of the order of fractions of nanometers. In this immediate vicinity of the electrode surface, matter is neither isotropic nor homogeneous. Considering the electrode/electrolyte interface, there is on neither side of it a well defined phase boundary. On the side of the electrode metal there is in atomar dimensions a certain change of electrical potential and charge density, that means an accumulation of negative charge at potentials negative to the potential of zero charge, E Epzc What follows on the solvent side in the direction perpendicular to the electrode surface is a relatively ordered but mobile sheet of solvent molecules and/or adsorbed species (ions or surfactive molecules) which is designated as the inner Helmholtz layer (IHL). A second less ordered sheet of solvent molecules which is called the outer Helmholtz layer (OHL) forms a smooth transition towards the fully established structure of the bulk solvent which is usually a mix of close range ordered clusters of solvent molecules being in long range statistical disorder (Fig. 4.1 a). The electronic charge on the metal side of the electrode is balanced by ionic countercharges in the vicinity of the electrode in the IHL and OHL and particularly in the so called diffuse part of the electrochemical double layer. In this diffuse part of the double layer a diffuse cloud of counter ions accumulates due to the coulombic interaction between the charged electrode and the charges of the different dissolved ions.
Published Version
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