Chemistry Reference
In-Depth Information
Electrical contact
Electrical contact
with ring electrode
Electrode
material
Ring electrode
material
Epoxy resin
(a)
(b)
1.6
Scheme of a cross section (in the length of the electrode) of
rotating-disc electrode (a) and a rotating-ring-disc electrode (b).
(with
N
the number of revolutions per second), and
c
is the concentration
of the compound in mol l
-1
.
Different methods are proposed in the literature to construct disc elec-
trodes, but the commonly used way is embedding a rod of the electrode
material in an insulating material such as glass, polyamides, acrlyates, epoxy
resins or polyvinylchloride. The electrodes used in the work described in
this topic were constructed by insulating the electrode material in epoxy
resin (Fig. 1.7). First, a copper piece was made with a hole for the position-
ing of the electrode material rod. This was positioned in a PVC holder,
which was then filled with epoxy resin. After curing for 48 h, the PVC mantel
was removed and the excess of epoxy scoured away on emery paper.
An alternative to disc electrodes is the ring-disc electrode (Fig. 1.6b). In
this type of electrode configuration, the disc electrode is surrounded by a
ring electrode, which is electrically isolated from the disc electrode. The
purpose of such an electrode is to study electrochemical reactions and their
mechanisms by detection of intermediates and reaction products at the ring
electrode which were formed at the disc surface. Owing to rotation, time-
independent limiting currents are obtained, and the radial convection
allows the reaction product of the disc to be transported to the ring.
However, it may be clear that only a fraction of the reaction product formed
at the disc will be transferred at the ring electrode. This fraction
N
is given
by the following equation and is called the collection efficiency
43
:
NII
=
[1.16]
RD
