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Randles–Ševčík Equation

Last Updated: 10/27/20 by Random Electrochemist

  • Sevcik,
  • peak current,
  • equation,
  • Randles-Sevcik,
  • Randles
Article Contents/Section Navigation
  1. Randles-Ševčík Equation
  2. References

1Randles-Ševčík Equation

In a voltammetric experiment where a potential sweep is applied to the working electrode using a potentiostat (e.g., LSV Linear Sweep Voltammetry (LSV) or CV Cyclic Voltammetry (CV) ), the peak current i_p observed for a voltammogram follows the Randles-Ševčík equation,
\displaystyle i_p=0.4463{\left( \frac{F^3}{RT}\right)}^{1/2}n^{3/2}AD_O^{1/2}C_O^*\upsilon^{1/2}
where F is Faraday's constant, R is the universal gas constant, T is the absolute temperature, n is the number of electrons involved in the redox half-reaction being studied, D_O is the diffusion coefficient for the redox active species, C_O is the molar concentration of the redox active species, A is the surface area of the electrode, and \upsilon is the rate at which the potential is being swept.
The Randles-Ševčík equation is often written in an abbreviated form under the assumption that the temperature is fixed at 298.15 K (25℃).  For work at this particular temperature, the constants appearing at the beginning of the equation can be combined, allowing the equation to be written more simply as follows:
\displaystyle i_p=(2.68648\times 10^5)n^{3/2}AD_O^{1/2}C_O^*{\upsilon}^{1/2}
The constant appearing at the beginning of this simplified version of the equation is understood to have units (e.g., 2.69 × 105 C mol-1V-1/2).
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