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Electro chemical studies on lead
acid batteries
By
M.SUDHEERA (Team Leader)
K.SIVA PRASADA RAO (Member)
P.ROHINIKUMAR (Member)
Regional Center: 1353 RVR & JC College of Engineering
(A)
Cyclic Voltammetry (CV)
Cyclic Voltammetry
•
Cyclic Voltammetry (CV) is a potentiodynamic electrochemical
measurement that is generally used to study the electrochemical properties
of an analyte in solution.
• In CV, the electrode potential ramps linearly versus time are known as
scan rates (Vs-1).
• The potential is applied between the reference electrode and the working
electrode and the current is measured between the working electrode and
the counter electrode.
Example for CV
A cyclic Voltammogram is obtained by measuring the current at the
working electrode during the potential scans.
Consider the following reversible reaction:
M+ + e-
M
The Cyclic Voltammogram graph resulting from the above single electron
reduction and oxidation.
Voltammogram of a Single electron oxidationreduction
c
d
a
b
e
g
f
From the graph
•
The reduction process occurs from (a) the initial potential to (d) the switching
potential. In this region the potential is scanned negatively to cause a
reduction.
•
The resulting current is called cathodic current (ipc). The corresponding peak
potential occurs at (c), and is called the cathodic peak potential (Epc). The Epc
is reached when all of the substrate at the surface of the electrode has been
reduced.
•
After the switching potential has been reached (d), the potential scans
positively from (d) to (g). This results in anodic current (Ipa) and oxidation to
occur.
•
The peak potential at (f) is called the anodic peak potential (Epa), and is
reached when all of the substrate at the surface of the electrode has been
oxidized.
Instrumentation
A CV system consists of
 Electrolysis cell
 Potentiostat
 Current-to-voltage converter and
 Data acquisition system.
The electrolysis cell consists of
 Working electrode
 Counter electrode
 Reference electrode and
 Electrolytic solution.
• The working electrode’s potential is varied linearly with time, while the
Reference electrode maintains a constant potential.
• The Counter electrode conducts electricity from the signal source to the
working electrode.
• The purpose of the Electrolytic solution is to provide ions to the electrodes
during oxidation and reduction.
• A Potentiostat is an electronic device which uses a dc power source to
produce a potential which can be maintained and accurately determined,
while allowing small currents to be drawn into the system without
changing the voltage.
• The Current-to-Voltage converter measures the resulting current, and the
data acquisition system produces the resulting Voltammogram.
Applications
• CV can be used to study qualitative information about electrochemical
processes under various conditions, such as the presence of intermediates
in oxidation-reduction reactions, the reversibility of a reaction.
• Used to determine the electron stoichiometry of a system, the diffusion
coefficient of an analyte (A substance whose chemical composition is to be
determined by chemical analysis).
• In addition, the concentration of unknown solution can be determined by
generating a calibration curve of current vs. concentration.