Tafel Analysis One-Electron Processes

For a fully electrochemically irreversible one-electron system, show how analysis of the voltammetry may yield information about the transition state for the process. 

When or , the Butler-Volmer equation reduces to the one-term Tafel equation as the first or second exponential term, respectively, may be approximated as zero. Consequently, a plot of In f vs — for the region highlighted in Fig. 2.3 (often called the Tafel region) should yield a straight hne of gradient aF/RT, so allowing measurement of the transfer coefficient (a), a (as shown in Eq. 2.1) is known as a transfer coefficient and is a measure of the position of the transition state between the oxidised and reduced species. Typically it has a value of around 0.5. 

Note that the data nearer the voltammetric peak reflect both electrode kinetics and diffiisional depletion, thus explaining the choice of data used to find a. 

4 Tafel Analysis Electrochemically Reversible Processes Problem 

For a fiilly reversible one-electron reduction, what gradient wiU be obtained for a plot of In / vs Assume that the redox species is confined to a thin layer such that 

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