Influence of nonlocal effects on kinetic parameters of heterogeneous charge transfer reactions

The influence of the spatial dispersion of the solvent and of the effect of the electrical field penetration into a metal on the free energy of the so lvent reorganization and the activation free energy for heterogeneous charg e transfer reactions is studied. The calculations are based on the exactly solved model of a sharp metal/electrolyte interface, the model of a Born sp here for the ion, and the three-mode approximation for the dielectric funct ion of the solvent. In the sharp-interface model, in the case of a mirror r eflection, a relationship for the dielectric tensor of a heterogeneous syst em comprising two contacting media with a plane interface is obtained, alon g with an expression for the potential created by a point charge. This expr ession formally coincides with the expression derived earlier by Vorotyntse v and Kornyshev, but it contains true bulk dielectric functions of contacti ng media. In the model of the Born sphere for the ion and the three-mode ap proximation for the dielectric function of the solvent, an expression for t he potential of image forces, which determines the dependence of the solven t reorganization energy on the distance from the reacting ion to the electr ode, is obtained. It is shown that both the reorganization energy and the a ctivation free energy decrease with decreasing distance from the ion to the electrode. The calculation results are compared with estimates of the reor ganization energy obtained from experimental data for the reaction Fe3+/Fe2 + and the reaction of the hydronium ion discharge.