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Linear Sweep Voltammetry: Introduction and Applications


Linear sweep voltammetry (LSV) is a simple electrochemical technique. The method is similar to cyclic voltammetry, but rather than linearly cycling over the potential range in both directions, linear sweep voltammetry involves only a single linear sweep from the lower potential limit to the upper potential limit.

Like cyclic voltammetry, linear sweep voltammetry uses a three electrode system. This consists of a working electrode, counter electrode, and reference electrode. The electrodes are placed in an electrochemical cell, which contains the solution of interest, and are connected to a potentiostat. The potentiostat controls the potential between the working and reference electrodes and measures the current at the working electrode so that a plot can be made that shows the electrochemical response (oxidation or reduction) of the material in question.

Applications


Using linear sweep voltammetry, several key parameters can be observed which can be used diagnostically to determine thermodynamic reversibility of a material. These parameters include the peak current (ip), the potential at the peak current (Ep), and the potential at half the peak current (Ep/2) prior to the peak being reached.

These will be interpreted here for the system O + e- ⇌ R, with R initially absent (i.e. assuming no coupled reactions). These values can be used to calculate key electrochemical parameters at the reversible and quasireversible limits.

The peak current

The peak current in amperes, ip, at 25 °C with bulk concentration O CO* in mol cm-3, electrode area A in cm2, the diffusion constant DO in cm2 s-1, and the scan rate v in V s-1 is given by:

For a reversible system K is 1, and for an irreversible system:

Graphs exist1, 2 to relate determine the degree of reversibility if α  is known.

The peak current potential

The peak current is given by:

In the reversible system Ξ = 1.109 where as in the irreversible system:

Graphs exist1,2 to relate determine the degree of reversibility if α  is known.

The half-peak current potential

The half peak current potential is given by the following formula:

For a reversible system ∆ = 2.20 , whereas for irreversible system:

Graphs exist1,2 to relate determine the degree of reversibility if α  is known.

Other Types of Voltammetry


  

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References


  1. A. J. Bard and L. Faulkner, Electrochemical Methods: Fundamentals and Applications, John Wiley & son, 2nd edn., 2001.
  2. H. Matsuda, Y. Ayabe, Z. Elektrochem., 1955, 59, 494-503.

Contributing Authors


  • Harry Robson
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