CYCLIC VOLTAMETRY
An electrochemical technique which measures the current that develops in an
electrochemical cell under conditions where potential is applied . CV is performed by
cycling the potential of a working electrode and measuring the resulting current..It is
based on Ohm’s law, E= IR. The current at working electrode is plotted against the
applied voltage.
Cyclic voltammetry is a versatile electrochemical technique which allows to study the
mechanics of redox and transport properties of a system in solution . The potential is
applied between the counter electrode and the working electrode and the current is
measured between the electrodes. In cyclic voltammetry, the direction of potential is
reversed at the end of the first scan.
For a redox reaction induced at a working electrode, the rate determining step is one of
the following individual step depending on the reaction: rate of mass transport of the
electro active species, rate of adsorption or desorption at the electrode surface, rate of
the electron transfer between the electroactive species and the electrode or the rate of
the individual chemical reactions. During the reducing scan, the surface conc. of species
Ox progressively decreases, resulting in an increased conc. gradient and a larger current.
As the reduction continues, the conc. of Ox at the electrode surface is depleted and the
current peak will decay if fresh Ox from the bulk solution doesnot have enough time to
diffuse to the electrode surface.When the direction of the potential is reversed, a peak
resulting from the reoxidation of reduced Red is observed
The applied potential controls the concs of the redox species at the electrode surface
(C0R and C0O), as described by the Nernst equation,
E=E0-RT/nF ln C0R/ C0O
R is the gas constant, T is the absolute temp, n is the number of es transferred, E0 is
the standard reduction potential of the redox couple.The important parameters in a
cyclic voltammogram are the peak potentials Epc and Epa and peak currents ipc and ipa
of the cathodic and anodic peaks, respectively.
If the electron transfer process is fast compared with other processes (such as diffusion),
the reaction is said to be electrochemically reversible and the peak separation is ΔEp =
|Epa- Epc| =2.303RT/nF.Thus, for a reversible redox reaction at 25oc.
ΔEp = 0.0592/nV or about 60mV for one electron
Irreversibility due to a slow electron transfer rate results in ΔEp > 0.059/nV greater
than 70mV for a one e reaction.
An electrochemical technique which measures the current that develops in an
electrochemical cell under conditions where potential is applied . CV is performed by
cycling the potential of a working electrode and measuring the resulting current..It is
based on Ohm’s law, E= IR. The current at working electrode is plotted against the
applied voltage.
Cyclic voltammetry is a versatile electrochemical technique which allows to study the
mechanics of redox and transport properties of a system in solution . The potential is
applied between the counter electrode and the working electrode and the current is
measured between the electrodes. In cyclic voltammetry, the direction of potential is
reversed at the end of the first scan.
For a redox reaction induced at a working electrode, the rate determining step is one of
the following individual step depending on the reaction: rate of mass transport of the
electro active species, rate of adsorption or desorption at the electrode surface, rate of
the electron transfer between the electroactive species and the electrode or the rate of
the individual chemical reactions. During the reducing scan, the surface conc. of species
Ox progressively decreases, resulting in an increased conc. gradient and a larger current.
As the reduction continues, the conc. of Ox at the electrode surface is depleted and the
current peak will decay if fresh Ox from the bulk solution doesnot have enough time to
diffuse to the electrode surface.When the direction of the potential is reversed, a peak
resulting from the reoxidation of reduced Red is observed
The applied potential controls the concs of the redox species at the electrode surface
(C0R and C0O), as described by the Nernst equation,
E=E0-RT/nF ln C0R/ C0O
R is the gas constant, T is the absolute temp, n is the number of es transferred, E0 is
the standard reduction potential of the redox couple.The important parameters in a
cyclic voltammogram are the peak potentials Epc and Epa and peak currents ipc and ipa
of the cathodic and anodic peaks, respectively.
If the electron transfer process is fast compared with other processes (such as diffusion),
the reaction is said to be electrochemically reversible and the peak separation is ΔEp =
|Epa- Epc| =2.303RT/nF.Thus, for a reversible redox reaction at 25oc.
ΔEp = 0.0592/nV or about 60mV for one electron
Irreversibility due to a slow electron transfer rate results in ΔEp > 0.059/nV greater
than 70mV for a one e reaction.
