  We propose an analytical model based on diffusion-reaction equation approach
for electrochemical electron transfer reaction, where the rate is limited by
the electron transfer process. The electron transfer from an ion in solution to
the metal electrode would occur as soon as the energy of the orbital on the ion
matches the Fermi energy of the metal and a new ion with more positive charge
is formed. Obviously the ion before electron transfer and the new ion, which is
formed after electron has transferred, moves under the influence of different
potentials. The coupling between these two potentials is assumed to be
represented by a Dirac Delta function. The diffusive motion in this paper is
described by the Smoluchowski equation. Our solution requires only the
knowledge of the Laplace transform of the Green's function for the motion in
both the uncoupled potentials. Our model is more general than all the earlier
models, because we are the first one to consider the potential of both the ions
explicitly.
