Hello Md. Monirul Islam ,

The value comes from a fully reversible limiting case of the Nernst equation, see Equations 2.58 to 2.61 in the 'Interpreting Electrochemistry' chapter that I attach for a detailed analysis and derivation of the value.

You may also find the other article I attach useful.

Hello Md. Monirul Islam ,

The value comes from a fully reversible limiting case of the Nernst equation, see Equations 2.58 to 2.61 in the 'Interpreting Electrochemistry' chapter that I attach for a detailed analysis and derivation of the value.

You may also find the other article I attach useful.

I agree with above answers. Let me put it in simple way,

∆Ep =│Ep anodic - Ep cathodic │= 2.3 RT/nF = 59/n mV at 298K

So basically 59 mV comes from Nernst equation and it is independent of scan rate. If potential difference ( ∆Ep) increases with increase in scan rate, it is characteristics of a slow electron transfer kinetics. Theoretically speaking it is important to get potential difference of 59 mV for a perfectly reversible reaction. However, the calculated value is always higher than 59 mV due to uncompensated solution resistance and non-linear diffusion. The peak separation can be improved by several ways such as cleaning the working electrode, auxiliary electrode must have higher area than working electrode, purging inert gas, distance between working and reference electrode, etc.

I hope it helps.

Thanks to all. I clearly understood from your reply and reading of the book entailed "Understanding Voltammetry, 3rd edition written by R. G. Compton et al"

Go back to the early work. You will see that the application of Nernest equation to a typical reversible electrochemical reaction was demonstrated only for liquid Mercury electrode.

Relevant replies here, but maybe I can add something. Although the number of electrons is > 1, 59 mV separation is seen because the electrons transfer as a cascade and the rate determining step has also only one electron. This is also seen in Tafel slopes. Peak separation < 59 mV indicates adsorption control. With quinones, for example, the peak separation can be as high as 200 mV but there the mechanism is rather complex, including proton transfer.

Hi Md. Monirul,

I agree with all the previous answers. Just to add some more comments, this value comes from considering the system a reversible one, with very facile kinetics. Electron transfer is so easy that there is no need to consider kinetic parameters. Then, the equation that have to be considered is this of equilibrium, Nernst equation. If you put the equation of the potential for Epa and for Epc and you make the difference you see that the formal potential is eliminated as well as the concentrations (in the log term). Then the value that remains is 2.3 RT/nF (2.3 comes from the conversion from ln to log function; R and F are the known constants and T is 298K (25ºC)). This gives 59/n (mV). In any case, the value also depends slightly on the value of the switching potential (varies from 57.0 to 60.5) as commented in the Table 6.5.1 (page 242 of Electrochemical Methods, Fundamentals and Applications, Bard and Faulkner , 2nd edition).

Good luck and best regards,