real potential of a species in a phase

Defined for species B in phase β as

$α B β = μ B β − z B F ψ β$

where $μ B β$ is the electrochemical potential of species B in phase β, $z B$ is the charge number of species B, $F$ is the Faraday constant, and $ψ β$ is the outer electric potential of phase β. Since $ψ β$ is zero when the charge on the phase β is zero, the real potential may be regarded as the value of the electrochemical potential of the uncharged phase.

Source:

PAC, 1974, 37, 499 (Electrochemical nomenclature) on page 506