Cyclic voltammetry principle

Cyclic voltammetry (cyclic voltammetry)

1. Basic principle: If an isosceles triangle pulse voltage is applied to the working electrode, the obtained current-voltage curve includes two branches. If the first half of the potential is scanned to the cathode and the electroactive substance is reduced at the electrode to generate a reduction wave, then when the second half of the potential is scanned to the anode, the reduction product will be oxidized again at the electrode to generate an oxidation wave.

Therefore, a triangular wave scan completes a reduction-oxidation cycle, so this method is called cyclic voltammetry, and its current-voltage curve is called cyclic voltammogram.

If the reversibility of electroactive substances is poor, the heights of oxidation wave and reduction wave are different and the symmetry is poor. The voltage scanning speed in cyclic voltammetry can be from a few millivolts per second to 1 volt. The working electrode can be a suspended mercury electrode, or a solid electrode such as platinum, glassy carbon and graphite.

2. The application of cyclic voltammetry

Cyclic voltammetry is a very useful electrochemical research method, which can be used to study the properties and mechanism of electrode reaction and the kinetic parameters of electrode process. But this method is rarely used for quantitative analysis.

(1) Determination of electrode reversibility The voltage scanning process in cyclic voltammetry includes two directions: cathode and anode, so the reversibility of the reaction of electroactive substances on the electrode surface can be judged from the peak height and symmetry of oxidation wave and reduction wave in the obtained cyclic voltammogram. If the reaction is reversible, the curve is symmetrical. If the reaction is irreversible, the curve is asymmetrical.

(2) Judgment of electrode reaction mechanism Cyclic voltammetry can also study electrode adsorption, electrochemical reaction products, electrochemical-chemical coupling reactions, etc. This is very useful for studying the redox mechanism of organic compounds, organometallic compounds and biological substances.