## Wikipedia - Sovratensione (elettrochimica) concentration overpotential

https://doi.org/10.1351/goldbook.C01230
The concentration @O04358@ of an @E01960@ at a given @E01952@ ($$\text{c.d.}$$) is basically the difference in equilibrium potentials across the @D01725@. More precisely, it is the potential of a @R05229@ (of the same @E01960@ as the @W06686@ ) with the interfacial concentrations which establish themselves at $$\text{c.d.}$$, relative to the potential of a similar @R05229@ with the concentrations of the bulk solution. From such a measured potential difference, with $$\text{c.d.}$$ flowing, one needs to subtract the ohmic potential drop prevailing between the two electrodes.
Source:
PAC, 1981, 53, 1827. (Nomenclature for transport phenomena in electrolytic systems) on page 1838 [Terms] [Paper]