The various electrochemical techniques that have been used to probe electrochemical reactions are discussed in detail in many excellent comprehensive texts and monographs. This Section is intended as an aid for those researchers who are interested in doing electrochemistry in RTILs, but do not have research experience or academic training in electrochemistry. Brief descriptions of some of the more popular techniques are described here along with references to examples of studies in ionic liquids where these techniques were effectively employed.

Cyclic voltammetry (CV) is widely
employed as a survey technique, i.e., it is the first technique that is
commonly applied during the preliminary analysis of an electrochemical system.
With the demise of analog signal generators, true analog sweep cyclic
voltammetry has been largely supplanted by cyclic staircase voltammetry (CSV).
This technique varies from analog sweep voltammetry in that the potential is
changed in small steps. As long as the step size is sufficiently small, the
theories developed for CV can be applied to CSV.^{321,335} The correct
analysis of cyclic voltammetric data is somewhat of an art, and there are many
examples of investigations where such CV data have been grossly overinterpreted
or misinterpreted altogether.

If the electrochemical reaction
(oxidation or reduction) is a simple diffusion-controlled process, i.e., an
electrochemically reversible or Nernstian system in which charge transfer is
very fast so that the reaction rate is limited by the rate of diffusion of the
soluble electroactive species to the electrode surface in the test solution,
then, the absolute magnitude of the voltammetric peak current, *i*_{p},
is given by the well known Randles-Sevick equation:^{321}

*n*3/2*F *3/2 1/2 * 1/2 *i*p =
0.4463 1/2 1/2 *AD C*ν
(6) *R T*

where *A* is the electrode area (cm^{2}),
*C*^{*} is the bulk solution concentration (mol cm^{-3}), *D*
is the diffusion coefficient of the electroactive species (cm^{2} s^{-1}),
*n* is the number of electrons involved in the reaction, *ν* is the
potential scan rate (V s^{-1}), and all of the other symbols have their
usual meaning. Linear plots of *i*_{p} as a function of *v*^{1/2}
that pass through the origin suggest that the system under study is diffusion
controlled. However, this is not a definitive test because the same behavior is
also observed for an irreversible electrode reaction.^{336}
Fortunately, there are other criteria that can be examined in order to verify
the reversibility of the system under study. For example, the peak potential
for the oxidation or reduction wave in question is independent of scan rate in
the case of a reversible system, but varies with scan rate for a
quasi-reversible or irreversible systems. Likewise, the nonlinearity of a plot
of *i*_{p} versus *ν*^{1/2} does not necessarily
indicate a slow charge transfer process. It may simply indicate that the
electrode reaction rate is governed by the rate of a chemical reaction
preceding the chargetransfer step.^{336} If *n*, *C*^{*},
*A*, and *T* are known and the system in question has been proven to
be electrochemically reversible, then *D* can be estimated from the slope
of a plot of *i*_{p} versus *ν*^{1/2} by using Eq.
(6).

For a reversible (Nernstian) reaction, the following criteria are valid

*E*pa − *E*pc =
(7)

*E*p − *E*p/2 =
(8)

*nF*

where *E*_{pa}, *E*_{pc},
and *E*_{p/2} are the anodic peak potential, cathodic peak
potential, and the appropriate half-peak potential, respectively. *E*_{p/2}
is simply the potential at 50% of *i*_{p}. When the reaction is
known to be reversible, the number of electrons involved in the reaction can be
estimated from Eqs. (7) and (8).^{321} Note, however, that Eq. (7)
varies slightly with changes in the voltammetric switching potential. Thus, Eq.
(8) is probably superior to Eq. (7) for estimating *n*. For a reversible
electrode reaction, the voltammetric half-wave potential, *E*_{1/2},
can be determined by estimating the potential at which 85.17% of the peak
current is observed.^{336} *E*_{1/2} can also be estimated
from the relationship given in Eq. (9):

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