Chemistry Reference
In-Depth Information
The above discussion concerns voltammograms
recorded at a fixed potential scan rate.
However, if the scan rate is altered we are likely
to observe a variation in the voltammograms
recorded. For example, when cyclic
voltammograms are recorded at a significantly
faster scan rate (more than 1 V s
−1
), a reversible
response in CV may be observed due to the time
taken to record the voltammogram. If the
potential scan rate is sufficiently fast it is
possible that no Ox formed according to
Eq. 2.4
has had time to chemically react while the
voltammogram is recorded. In this case, we can
estimate a thermodynamic potential such as the
formal potential from the obtained reversible
voltammogram.
Although the half-peak potential (
E
p/2
) is often
confused with the half-wave potential (
E
1/2
), it
is defined as the potential where the current is
half of the peak current in CV. In addition, the
relationship between
E
p
and
E
p/2
is
represented by
Eq. 2.6
:
(2.6)
where
n
is the number of electrons involved in
the redox electrode reaction. However,
E
p/2
is
not an important thermodynamic parameter,
and hence it is not used very much.
The half-wave potential (
E
1/2
) is the potential at
which the wave current in steady-state
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