The molar species fluxes, Ni (SI unit: mol/(m2·s)), perpendicular to an electrode-electrolyte interface are calculated by summing all the flux contributions from the electrode reactions, of index m, according to Faraday’s law:

where im is the local current density (SI unit: A/m2) of the electrochemical reaction, nm the number of participating electrons and F (SI unit: C/mol) is Faraday’s constant.

The molar species flux, Ni, is obtained from normal component of the molar species flux vector over the electrode-electrolyte interface:

where n is the normal vector of the boundary pointing into the domain.

where av,m, (SI unit: m2/m3) is the specific surface area.