Chemistry Reference
In-Depth Information
•The surface of the counter electrode should be at least ten times greater
than the surface of the working electrode. The aim is to study the half
reaction occurring at the working electrode. This means that this half
reaction should be the slowest, as otherwise the properties of the
half reaction occurring at the counter electrode will determine the char-
acteristics of the measured electrical current. By using a much bigger
surface, this problem is circumvented because the reaction rate is depen-
dent on electrode surface. Therefore, a relatively slow half reaction at
the counter electrode is occurring much faster still than the one at the
working electrode because more species are transformed per time unit
owing to the much bigger surface that is available for the half reaction
at the counter electrode.
•The counter electrode should be a good electrical conductor. This con-
dition is clear; if the counter electrode is not a good conductor, it means
that a poor amount of current can pass the interface at the counter elec-
trode, which will then determine the measured current of the electro-
chemical cell. Therefore, the measured current will provide information
about the properties of the counter electrode and not about the half
reaction occurring at the surface of the working electrode.
•The positioning of the counter electrode against the working electrode
is very important
3
.
1.6.3
The reference electrode
Reference electrodes were discussed in section 1.5, and Table 1.1 presented
commonly used and commercially available reference electrodes.
1.6.4
The working electrode
The working electrode is the one where the reaction to be studied occurs
and is constructed of an electrically conductive material. The commonly
used materials are platinum, gold and glassy carbon, which are available in
a wide range of shapes, purity and configuration, and will be discussed in
this section.
Materials
Platinum and gold
Platinum
7-11
and gold
12-16
are the most commonly used electrode materials.
The reason can be found in their ease of manufacture, variety of configu-
rations and the commercial availability of these configurations (rod, wire,
microwire, sheet, woven structures) and on their high purity. Despite their
