Technical note

The role of Counter electrode

For a system using a three-electrode potentiostat, we measured current when a potential is applied between the working electrode and the reference electrode. Passage of current through an electrical circuit requires electron transfer reaction between the working electrode and the counter electrode.
The main function of the counter electrode is to provide the location of the second electron transfer reaction. Important parameter of the counter electrode is the surface area. It is required (area) large enough to support the current generated for the working electrode. For example, the surface area of the platinum electrode of 5 cm is sufficient to use as an electrode, such as steady-state cyclic voltammetry experiments. However, for generating a high current measurements such as bulk electrolysis, the counter electrode of a larger area is required, as Catalog No.012961 which the length of platinum is 23 cm. This electrode is used for measurement, such as rotating ring disk.
The cell shape is also an important point. For the electrolysis, to avoid the contamination of the product from the counter electrode, it is arranging separately, isolated in a chamber, from the working electrode. For electrochemical measurements such as cyclic voltammetry, because of the short measurement time, you can ignore the effects of contamination by electrolysis. Therefore, it is not usual the isolation of the counter electrode. In some cases, the separation of the counter electrode in a chamber, increases the resistance between counter electrode and reference electrode, under the influence of (sintered glass) fritz. However, in the case of bulk electrolysis, because of long measurement time, the agitation and separation of the working electrode and counter electrode using a chamber is necessary, to prevent the transportation between two electrodes.