Faradaic current density and the Butler-Volmer equation

Faradaic current density and the Butler-Volmer equation 

As the reactions take place at the interface, a value that is frequently used for electrochemical components is the current density j, with 1 being the current of the cell and S the geometric surface area of the electrode. In view of the usual 

Consider the notations of the redox reaction [1.1], with and being the reaction constants respectively in the directions of oxidation and reduction [DIA 96]. 

The Faiadaic current density of the electrode, i.e. the flow of electrons toward the electrode, is coimected to the rate of appearance of the electrons (in the direction of oxidation) and the rate of their disappearance (in the direction of reduction)  

The reaction rates depend on the activities of the oxidizing and reducing species flOx at the electrode/electrolyte interface, and on the reaction constants 

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