Abstract: The theoretically derived expressions of the current density, the height and width of the potential barrier are presented based on the thermal activation model and Schottky effect.The calculated results show that the height and width of the potential barrier decrease with increasing over-potential. It follows that the rate of successful electron transfers does not only depend on the number of particles on the solution side of the metal-solution interface which exist in appropriate quantum states but also on the height and width of the potential barrier.