Preceding chemical CE reactions

The preceding chemical reaction causes the concentration of the electroactive A, to be lower than otherwise the effect of this will be largest when K is large, when a purely kinetic current dependent on the value of fe] will be observed. 

Modification of the convective-diffusion equation involves addition of terms to take account of the preceding reaction. Thus, for the rotating disc electrode, we obtain 

We also consider first the case where fe, is large, such that the reaction layer concept is useful. For the transport limited current, imax, we have the further boundary condition 

Solution proceeds via addition of the two convective-diffusion equations and leads to the result [151], assuming a rapid chemical reaction 

A plot of imax oo 1/2 vs. imax yields kx. If the chemical reaction is very rapid kr large), the slope of the plot will be zero [see Fig. 13(a)]. 

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