Cyclic Voltammetry
Definition and meaning of Cyclic Voltammetry in chemistry.
Cyclic voltammetry is an electrochemical technique in which the potential applied to a working electrode is swept linearly forward and then reversed back to its starting value, while the resulting current is recorded to reveal the redox behavior of a chemical species in solution.
In more detail
A three-electrode cell (working, reference, and counter electrode) is used so that oxidation or reduction at the working electrode can be measured without disturbing the reference potential. As the potential scans past a species' redox potential, current rises to a peak as the analyte is oxidized or reduced at the electrode surface, then falls as it is depleted near the surface; reversing the scan direction produces a corresponding peak for the reverse reaction. The resulting current-versus-potential plot, called a voltammogram, reveals whether a redox couple is electrochemically reversible, how many electrons are transferred, and the rate of electron transfer. Chemists use it to characterize new compounds, study reaction mechanisms, and evaluate materials for batteries and sensors.
Key facts
| Field | Analytical Chemistry |
|---|---|
| Electrode setup | Working, reference, and counter electrode |
| Output | Voltammogram (current vs. applied potential) |
| Reversible ΔEp (n = 1, 25°C) | ~59 mV |
Running cyclic voltammetry on ferrocene in acetonitrile with a supporting electrolyte gives a symmetric, reversible one-electron voltammogram for the Fc/Fc+ couple, with a peak-to-peak separation near 59 mV at 25°C, so it is commonly used as an internal reference standard.
Frequently asked questions
What does the peak-to-peak separation in a voltammogram indicate?
For a fully reversible one-electron redox couple it is theoretically about 59 mV at 25°C; larger separations signal slower electron-transfer kinetics (quasi-reversible or irreversible behavior).
Why does scan rate matter in cyclic voltammetry?
For a diffusion-controlled reversible process, peak current is proportional to the square root of scan rate (the Randles-Sevcik relationship), so varying scan rate helps distinguish diffusion control from adsorbed or chemically coupled electrode processes.