Randles - Sevick equation provides an area value of the working electrode. Is this area the true electroactive surface area of the working electrode or there are some condition-boundations to the use of the Randles-Sevick equation during determination of electrode surface area.
If there's any mass transfer from the bulk involved (diffusion and/or convection), it's the geometrical area.
R-S equation only applies if the process is reversible. This is an important drawback in many experiments.
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What is the material of the electrode? If it is a noble metal like Au or Pt you can easily check the real surface area by looking at adsorption processes. If it is a non noble metal like carbon, then you can use the Randles-Sevik equation using a very fast reversible redox couple such as RuHex, Ferro/Ferri cyanide I would not recommend it as it has some slower kinetics and may interact with your surface. The other experiment you can do is to check the capacitance as a function of scan rate, as this will only depend on the charge of the double layer and no faradaic contributions. Just choose a region where current is nearly zero.
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