Amber Beigel
Independent Research
Cyclic Voltammetry
January 20, 2012
Cyclic Voltammetry
Cyclic voltammetry is an electroanalytical technique used to study electrochemical reactions. There are many different types of electroanalytical techniques such as linear sweep voltammetry, staircase voltammetry, chronocoulometry, chronoamperometry, etc. Cyclic voltammetry though is the most often used electroanalytical technique and possibly the most popular. This is due in part to the fact that a lot of information can be determined about a solution through cyclic voltammetry and the technique is quite simple. Electrochemists are not the only chemists that use this technique. Organic chemists, inorganic chemists, analytical chemists, and others use this technique for various things that they are studying. Inorganic chemists, for example, use cyclic voltammetry to study the effects of ligands on the oxidation/reduction potential of the central metal ion in complexes.
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The equipment involved in cyclic voltammetry is quite simple also. It consists of a conventional three-electrode potentiostat connected to three electrodes that get immersed into a solution.
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The three electrodes are known as a working electrode, a counter electrode, and a reference electrode. A computer is typically used to record the cyclic voltammogram as a graph of current versus potential (see figure 1). Charge flows through the working electrode and the counter electrode. Potential is applied between the working electrode and the reference electrode, but the current is measured between the working electrode and the counter electrode. The computer then plots the current versus potential.
Potential that increases or decreases with time, is applied to the working electrode.
Current flows through the electrode that either oxidizes or reduces the analyte in solution while potential is swept back and forth past the formal potential, E o
. The magnitude of the current

Amber Beigel
Independent Research
Cyclic Voltammetry
January 20, 2012 observed is proportional to the concentration of analyte in solution and because of this; cyclic voltammetry is very useful in determining concentrations of a solution.
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The potential is plotted on the x-axis while the current is plotted on the y-axis (see figure
1). Potential is measured in volts and current is measured in amps. The cathodic peak (positive peak) represents the analyte when it is being reduced. The anodic peak (negative peak) represents the analyte when it is being oxidized. The peaks observed when the sweep is reversed have the same shape as the forward sweep, but are upturned because the direction of the current flow is reversed.
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The electrode potential ramps linearly versus time and this ramping is known as the scan rate which typically has the units V/s or mV/s. In general, the scan rate used in an experiment can range from 0-200 mV/s depending on the potentiostat instrument being used.
Several sweeping segments should be used because the first couple of sweeping segments are typically not very useful or meaningful.
As mentioned before, there are three electrodes involved in cyclic voltammetry; a working electrode, a counter electrode, and a reference electrode. Before and after each experiment, one should thoroughly wash each electrode with deionized water to ensure that the experiment is not altered or ruined in any way. The working electrode can include such things as gold, platinum, or glassy carbon. The counter electrode can be made of any material that conducts easily and won’t react with the solution. A common counter electrode used is a platinum wire electrode. The reference electrode is more complex than the others. One reference electrode known to be used is an Ag/AgCl reference electrode. Together, these three electrodes provide the information needed for a cyclic voltammogram.

Amber Beigel
Independent Research
Cyclic Voltammetry
January 20, 2012
A lot of information can be obtained from a cyclic voltammogram which is why it is very useful. The information obtained can be both quantitative and qualitative. One can determine if there are intermediates in oxidation-reduction reactions, if a reaction is reversible or not and if it is reversible, to what extent. The diffusion coefficient of the analyte or analytes in solution can be determined and the formal reduction potential can also be determined. As mentioned before, the concentration of analyte in solution can be determined as well because the concentration is proportional to current. In this sense, the concentrations of an unknown in solution could be determined which is very useful.
In conclusion, cyclic voltammetry is very useful to chemists when used correctly. The information that can be found is important and useful. A lot of research in electrochemistry being done right now involves the proper use and analysis of cyclic voltammetry and will continue to do so in the future.

Amber Beigel
Independent Research
Cyclic Voltammetry
January 20, 2012
Figure 1: Figure 1 shows a typical cyclic votammogram. Notice the two defined peaks (cathodic and anodic peaks). Current is plotted against potential. A lot of information can be determined from a cyclic voltammogram.

Amber Beigel
Independent Research
Cyclic Voltammetry
January 20, 2012
References
1.
Mabbott, Gary A. “An Introduction to Cyclic Voltammetry.”
Journal of chemical
Education . 60.9. 1983: 697. Web. 20 Jan. 2012.
2.
Educator’s Reference Guide for Electrochemistry. Pine Instrument Company: Grove
City, Pennsylvania, 2000. Pages 22-24.