Voltammetry and Scan Rate Effects

Cyclic voltammetry (as shown in Fig. 4.4 where the current has been normahsed with respect to the square root of the scan rate) was recorded for a compound A (with D = 10 cm s ) at a large electrode, at scan rates ranging from 2 mV s to 2 V s . Account for the observed change in voltammetry. Is it possible to infer any kinetic information from these data  

At the lowest scan rates, the voltammetry is unaltered with scan rate, except for the current scaling by vi. The scan rate is sufficiently slow that the kinetics of 

The Matsuda-Ayabe parameter. A, quantifies kinetic reversibility for an electrochemical process  

At the point of transition between reversible voltammetry and quasi-reversibiUty, A 15. Therefore for the lower two scan rates, we can infer that A 15. For the faster two scan rates, the behaviour is quasi-reversible so we expect that the Matsuda-Ayabe parameter is 15. 

Given that the transition occurs at approximately 50 mVs , by substitution  

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