Kinetic treatment based on exchange current

The Tafel law can be corrected for transport effects, enlarging the region of the voltammetric curve that can be utilized in Tafel plots. 

As this is the Nernst equation, the value of E can be identified with the equilibrium potential Eeq. Knowing [0]oc and [R x we can determine k0 from the intersection of the two straight lines, in the same way as demonstrated in Fig. 6.8. 

All the equations deduced above can be formulated in terms of the exchange current I0 (Section 4.5). In this way we have the advantage of obtaining the current as a function of the difference in applied potential and equilibrium potential, i.e. the overpotential, rj the disadvantage is that it is not directly related to the rate constants, which is important for comparison with other branches of kinetics. 

As shown in Chapter 4, the exchange current density is equal to the anodic or cathodic component of the current density at equilibrium (7a= -7c=/o) that is 

For an irreversible reaction and for overpotentials corresponding to the exponential region, the Tafel law is 

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