Chemistry Reference
In-Depth Information
25
20
15
10
5
0
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
Concentration (mol l
-1
)
4.2
Nature of the relation between current density and hydrogen per-
oxide concentration observed for different rotating-disc electrode
materials with a rotation speed of 16.67 rotations per second.
with the reference electrode is smaller than the potential applied by the
potentiostat.
This ohmic potential drop can be reduced in two ways: either by lower-
ing the cell resistance or by decreasing the measured electrical current. The
resistivity or specific resistance cannot be modified in this research because
it is set according to the composition of the bleaching solution. The absolute
resistance can be diminished in principle by putting the working electrode
and the reference electrode (using a so-called Luggin capillary tube) closer
to each other. Applying this has led in practice to a slight improvement, yet
totally insufficient to solve the problem.
The current signal, on the other hand, can be reduced drastically. A first,
obvious, method is reducing the working electrode surface. A second pos-
sibility involves reducing the amount of reacting electroactive component
which is transported to the electrode surface, e.g. by means of a membrane
or a porous wall. When the working electrode, the reference electrode and
the counter electrode are positioned at the same side of the membrane, the
resistance of the solution between the electrodes is not influenced by the
membrane, which is not the case when the electrodes are positioned at dif-
ferent sides of the membrane, and the influence on the IR voltage drop can
