This Demonstration gives Faradaic (

) and electrode impedance (

*Z*) for the equivalent circuit (Randles circuit) of the electrochemical redox reaction (

) at a rotating disk electrode (RDE), taking into account the series ohmic resistance

, with

where

is the angular frequency.

is the charge transfer resistance,

the mass transport resistance,

the interfacial double capacitance,

the time constant of the mass transport,

the characteristic frequency of charge transfer, and

the characteristic frequency of mass transport.

[1] J.-P. Diard, C. Montella, and B. Le Gorrec,

*Cinétique Electrochimique*, Paris: Hermann, 1996.

[2] C. Montella, J.-P. Diard, and B. Le Gorrec,

*Exercices de Cinétique Electochimique, II Méthodes d'impédance*, Paris: Hermann, 2005.

[3] M. E. Orazem and B. Tribollet,

*Electrochemical Impedance Spectroscopy*, Hoboken, NJ: John Wiley & Sons, 2008.