Fundamental Principles of Organic Electrochemistry: Fundamental Aspects of Electrochemistry Dealing with Organic Molecules - Fundamentals and Applications of Organic Electrochemistry - page 22

voltammetry is equal to half of the diffusion
limiting current ( Figure 2.6a ). E 1/2 is equal to
the formal potential of the studied electrode
reaction when the reaction is a redox reversible
process and the diffusion coefficients of the
oxidized and reduced forms of a studied species
are equal to each other. However, if the reaction
involves a chemical reaction subsequent to
electron transfer, E 1/2 is no longer equal to the
formal potential ( Figure 2.6b ).
Figure 2.6 Steady-state voltammograms of a
simple redox system (a) without and (b) with
following chemical reaction
The decomposition potential ( E dec ) is a
potential where the Faradic current begins to be
observed on the voltammogram and is also
called the onset potential ( E onset ). Although
E dec is often used as the thermodynamic index
for the oxidation/reduction of the studied
species, it is not exactly a thermodynamic
parameter.