cathodic transfer coefficient, αc

For a reaction with a single rate-determining step

$α c ν = − R T n F ( ∂ ( ln ( | I c | ) ) ∂ E ) T , p , c i , ...$

where $α c$ is the cathodic transfer coefficient (number), $R$ is the gas constant, $T$ is the thermodynamic temperature, and $ν$ the stoichiometric number giving the number of identical activated complexes formed and destroyed in the completion of the overall reaction as formulated with the transfer of $n$ electrons.

Source:

PAC, 1974, 37, 499 (Electrochemical nomenclature) on page 515