Further developments on the theory of electron transfer across the electrode/electrolyte interface

The Anderson-Newns model is generalized and applied to investigate several processes of heterogeneous electron transfer across the solid/electrolyte interface. For adiabatic semi-conductor/electrolyte electron transfer to an acceptor analytical expressions for adiabatic free energy profiles (AFEP\u27s) are produced and analyzed for a wide range of system parameters. Perturbations of semiconductor electronic bands are considered and shown, by model calculations, to result in significant modification of AFEP. In particular, they result in a three-well shaped AFEP despite the linear response theory used to describe the solvent. For the transfer of multiple electrons to a set of interacting acceptors the solvent is described by a set of collective coordinates; using Hartree-Fock linearization of the Anderson Hamiltonian, electronic energy of the system is obtained. Adiabatic free energy surfaces (AFES\u27s) for the case of two acceptors are generated by analytic parametric representation and self-consistency looping. Various reaction pathways across the AFES are discussed. Interionic distance and local electrostatic potential are shown to affect AFES significantly. Sequential and parallel transfer of electrons to an acceptor with multiple levels is considered and analytical expressions for the electronic energy for two and three level cases are derived. Three-well shaped AFEP\u27s for two-level case are generated and analyzed. The relative contribution of sequential and parallel electron transfer is shown to depend on a number of system parameters so no general preference can be drawn. It is shown that external bias significantly distorts the shape of AFEP and thus the double layer effects influencing the bias may result in significant distortion of the kinetics of both sequential and parallel electron transfer. The effect of perturbations of the electronic bands of the metal on nonadiabatic metal/electrolyte electron transfer is outlined using Marcus-Dogonadze-Kuznetsov theory for analysis of reaction free energy dependence of transfer coefficient and inhomogeneity factor. It is shown that perturbations affecting the electronic spectrum at the solid/liquid interface may significantly influence kinetics of the process