KINETICS OF ELECTRODE REACTIONS_2

if we begin the reaction at the potential Q1 and reduce it to Q2 as shown in Figure 2. The activation energy for process 1 is Gc1 and Gc2 for process 2. The formula is in equation (8)

                     (8)


the subscript c indicates a cathodic process. The activation energy in the anodic direction is described in equation (9).

                     (9)


Bheta is the symmetri factor. This factor can vary between 0 and 1. It is the fraction of potential across the double layer to promote reaction. The form of kinetic expression for chemical reactions is (equation (10)).

                        (10)



G* is the free energy of activation and k' is a constant. The rate of an electrochemical reaction is proportional to the current density as described in equation (11).

                       (11)


r is reaction rate (mol/s cm2), c is the reactant concentration (mol/cm3). For anodic reaction involving a single electron transfer, the rate is expressed in equation (12).

                      (12)





therefore equation (12) transform to equation (13)

                                                  (13)


similarly, the rate equation for cathodic reaction is in equation (14)

                                                  (14)


The net reaction rate is the difference between the rate of anodic and cathodic reaction, as depicted in equation (15)

                   (15)