200 400
Potential (mV)
D
reversed (decreased), and the current continues to decay. As the redox potential is approached, a
net reduction of the oxidized species takes place resulting in the appearance of a peak-shaped
cathodic current (D).
I
r,
600
Figure 2-7. Basic shape of the current response for a cyclic voltammetry experiment.92
In the presence of a reversible redox system, that is for fast electron transfer processes at
the electrode (reaction kinetics fast compared to the scan rate), the surface concentrations of the
oxidized and the reduced species are maintained at the values required by the Nernst equation (2-
10):
RT C,
E = E" + -In( )
nF CT
(2-10)
where E is the electrode potential, Eo is the standard potential of the redox couple, R is the
universal gas constant (8.314510 J K^1 mol- ), T is the temperature in K, n is the number of
electrons transferred in the half reaction, F is the Faraday constant (9.6485309x104 C mOl-1), and
-10 08