Changing Scan Rates

A researcher can learn a lot about the analyte from collecting multiple CVs at different scan rates. In order to create a trustworthy plot of the changes at different scan rates, it is necessary to collect CVs at 5 – 6 different scan rates and save them for later analysis. A very quick qualitative check of the electrochemical reversibility of a wave can be made as the CVs are collected. An electrochemically reversible wave (fast electron transfer rate) will have the same E_p’s at every scan rate,

While the observed current will increase with increasing scan rate, the peak potentials (Ep’s) of a reversible wave will not change.

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whereas an electrochemically irreversible feature (slow electron transfer rate) will have E_p’s that drift to more extreme potentials with increased scan rate.

Both the observed current and the peak potentials (Ep’s) of an irreversible wave will not change. The Ep’s will tend to shift toward more extreme potentials with increasing scan rate.

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Standard Operating Procedures for Cyclic Voltammetry by Daniel Graham
is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.