Electrostatic potential distribution electrical field effects

The effect of the dielectric properties of water on the EDL structure is seen by the electrostatic potential profiles shown in Eigure 2.5, which were obtained by solving Equations 2.2 and 2.3 with a combination of different dielectric models for one-electron reduction of a —1 valence reactant at spherical electrodes of different radii. The uniform dielectric constant of 78 and the 3-state model give electrostatic potential distributions that exhibit much less electrode size dependence than that predicted by the Booth model. This is because the Booth model allows flexible variation of dielectric constant and electric field strength in the calculation, whereas in the uniform and 3-state models, the dielectric constants are fixed. The Booth model gives very similar linear potential distribution in the compact EDL at large electrodes to that predicted by the uniform dielectric model, while its prediction for very small electrodes is close to that of the 3-state model, which produces a very steep potential drop inside IHP and a somewhat dragging... 

A very pronounced double-layer effect is also observed in the voltammetry of adsorbed outer-sphere reactants." For instance, the voltammetry of self-assembled monolayers (SAMs) of alkane-thiols containing a terminal redox group (e.g., ferrocene) is strongly influenced by the electric field across the SAM, and this is manifested in peak broadening and a shift in the half-wave potential. Because redox-active SAMs are frequently geometrically very well defined, and their dielectric properties can be measured, the electric field across these layers can be readily computed from electrostatics to obtain the electric potential at the redox center. This in turn can be used to compute the influence of the electric potential distribution on voltammetric response, which can then be quantitatively compared to experiment. 

The anion-cation bond-breaking produced by the formation of a surface is responsible for several phenomena. Some have an electrostatic origin. This is the case for polarization which is induced by surface electric fields which are much larger than those in the bulk. This is also the case for shifts of the renormalized atomic energies of surface atoms and shifts of surface bands, which are induced by reduction of the Madelung potential at the surface. On the other hand, as far as covalent effects are concerned, a modification of the anion-cation hybridization takes place, due to the lower coordination of the surface atoms. This has important consequences on the gap width and on the electron distribution. 

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