Rate Equation for Consecutive Electrochemical Reactions

The first term in Eq. (31) is the cathodic term, negative by convention (see footnote b), that contains the activity of the initial reactant, Ai. For simplification, 7), which is the total number of electrons transferred prior to the rds, has replaced the summation term in the argument of the exponential of Eq. (29). The second term in Eq. (31) is the anodic direction term, giving a positive current contribution, which contains the activity of the overall product of the reaction, A +1, and 7/ is the number of electrons transferred following the rds. 

Grouping potential-independent terms into an exchange current density and collecting the arguments of the exponentials simplifies the rate equation to 

This is obviously a BV type of equation [see Eq. (20)], but where P and (1 - P) in that equation have become replaced, respectively, by transfer coefficients which are 

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