A number of different analytical expressions for iloc,m are available. In the following the index
m is dropped. All parameters are understood to refer to a specific reaction.
where Eeq denotes the equilibrium potential.
where αc denotes the cathodic charge transfer coefficient,
αa the anodic charge transfer coefficient.
where αc denotes the cathodic charge transfer coefficient,
αa the anodic charge transfer coefficient,
i0 the exchange current density, and
η the overpotential.
where Aa (SI unit: V) is the so-called Tafel slope. The cathodic Tafel expression is according to:
where CR and
CO are dimensionless expressions, describing the dependence on the reduced and oxidized species in the reaction.
where k0 (m/s) is the heterogeneous rate constant.
where iexpr (A/m
2) is the current density expression in the absence of mass transport limitations for the species, and
ilim (A/m
2) is the limiting current density that corresponds to the maximum transport rate of the species. The derivation of this expression assumes either a strictly anodic or an cathodic reaction.