Part 1: Cyclic voltammetry - I

1. Potential sweep technique (Potentiodynamic method)

The potential sweep technique refers to a measurement of the current change in function of the time (this is called “potential sweep” or “potential scan”) by changing the potential (applied potential) to the working electrode over time. If the sweep direction is one direction only, it is called linear sweep voltammetry. Once the potential is swept, the sweep direction is reversed to continue the potential sweep, and repeat the reversal, it is called cyclic voltammetry. The result is usually displayed as a current-potential curve (voltammogram) by combining two time-varying parameters (current, potential). At this time, the voltammetric response current represents the response to the applied potential of the electrode reaction, as well as the time course of the electrode reaction as in chronoamperometry.

2. Three electrodes electrochemical cell and current direction

Basically, in this voltammetric technique, three types of electrodes are connected to the potentiostat as shown in Fig. 1.2. The current flowing between the working electrode and the counter electrode is detected while controlling the electrode potential of the working electrode with respect to the potential of the reference electrode. This is done by detecting the current flowing between the two electrodes. When an oxidation reaction occurs at the working electrode interface, electrons flow from the working electrode to the counter electrode from the external circuit connected to the potentiostat, so current flows from the counter electrode to the working electrode.

A Orientation direction of response current flow during oxidation.
B Orientation direction of electrons flow during oxidation.

Fig. 1-2 Potentiostat and electrode connection