Thermodynamic Analysis of the Symmetry Factor and the Transfer Coefficient in Electrode Kinetics

Contemporary thermodynamics using the transformed Gibbs energy for electrochemical systems is applied to activated one‐electron transfer processes. The symmetry factor is treated as the fractional charge transferred to the electrode in oxidation, or from the electrode in reduction, in order to reach the transition state. Allowance is made for the variation of the symmetry factor with the inner potential at the reaction site where activated complexes are formed. On this basis, new exact equations are developed for the dependence of the standard (electrochemical) Gibbs energy of activation on the overpotential, temperature, and pressure. Within the new framework, the understanding of the effects of potential and temperature on the transfer coefficient and the meaning of "ideal" and "real" activation enthalpies, are clarified.