ECE Mechanism at a Microdisc Electrode

Assuming a value of D = 2.1 x 10 cm s estimate a value for k and suggest a mechanism for the electrode reaction. 

The variation arises since for a very small electrode the convergent/ divergent diffusion to and from the electrode is extremely effective, and so species B is removed from the electrode before there is time for the species to undergo reaction to form C and then gain a second electron. Hence in the re 0 limit, n ff 1. 

In contrast, for a very large electrode the diffusional transport is much less effective and so B can remain near the electrode long enough to undergo decomposition into C and hence further reduction and so in the limit of 

Alternatively, a graphical approach can be taken in which the experimental current values are converted into eff using Eq. 5.4 and then ( eff 1) is plo tted against r. The straight line graph intersects the y-axis close to unity and has a slope of (4/7r)(U/A )2, allowing the determination of k. 

Note that digital simulation of the full voltammetric waves has superseded the use of approximate equations in electrochemical research. 

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