Overview

Source: Laboratory of Dr. Kayla Green — Texas Christian University

A Cyclic Voltammetry (CV) experiment involves the scan of a range of potential voltages while measuring current. In the CV experiment, the potential of an immersed, stationary electrode is scanned from a predetermined starting potential to a final value (called the switching potential) and then the reverse scan is obtained. This gives a 'cyclic' sweep of potentials and the current vs. potential curve derived from the data is called a cyclic voltammogram. The first sweep is called the 'forward scan' and the return wave is called the 'reverse scan'. The potential extremes are termed the 'scan window'. The magnitude of reduction and oxidation currents and the shape of the voltammograms are highly dependent on analyte concentration, scan rates, and experimental conditions. By varying these factors, cyclic voltammetry can yield information regarding the stability of transition metal oxidation state in the complexed form, reversibility of electron transfer reactions, and information regarding reactivity. This video will explain the basic setup for a cyclic voltammetry experiment including analyte preparation and setting up the electrochemical cell. A simple cyclic voltammetry experiment will be presented.

Procedure

1. Preparation of Electrolyte Solution

Prepare an electrolyte stock solution (10 mL) composed of 0.1 M [Bu₄N][BF₄] in CH₃CN.
Place the electrolyte solution in the electrochemical vial, add a small stir bar, and place the cap onto the vial as shown in Figure 1.
Check to ensure that the nitrogen lead is in the electrolyte solution. Stir and degas the electrolyte solution with a gentle stream of dry N₂ gas (~10 min) to remove redox

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Results

A CV scan of ferrocene at 300 mV/s in acetonitrile was carried out and the corresponding voltammogram is shown in Figure 2.

The ΔE can be derived from the data in Figure 2 based on the difference between E_pa and E_pc.

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References

Bard, A. J., Faulkner, L. A. Electrochemical methods: Fundamentals and Applications. 2nd ed. New York: Wiley; 833 p. (2001).
Geiger, W. E., Connelly, N. G. Chemical Redox Agents for Organometallic Chemistry. Chem Rev. 96 (2), 877-910, (1996).