https://doi.org/10.1351/goldbook.C01458

If several reactions take place simultaneously at the electrode a partial electrode current density (c.d.) jk can be assigned to each reaction. It is given by the stoichiometry of the reaction and by the amount of substance of **B** reacting (per unit time and per unit electrode area) in the reaction considered. The current efficiency of reaction k, ɛk is defined as the ratio of jk to the total c.d.: \[ɛ_{k}=\frac{j_{k}}{\sum _{\begin{array}{c}
m
\end{array}}j_{m}}\] Note that ɛk may be larger than one if cathodic and anodic reactions take place simultaneously at the same electrode. However, ɛk still gives correctly the product yield, which is the quantity of industrial interest. The product yield is the amount of substance of **B** produced per unit charge and is equal to ɛk.νB,k/nk.F (in the absence of a chemical reaction which is consecutive to the electrode reaction and which consumes or produces species B). n k is the charge number of electrode reaction k. Note that in the case of simultaneous electrode reactions the distribution of the partial c.d. jk may be different from that of the total c.d., i.e. the function (jk)x/j = fk(x) may be different from jx/j = f(x). In electroplating the term 'metal distribution' is sometimes used to designate the distribution fk(x) of the partial c.d. for metal deposition.*Source: *

PAC, 1981,*53*, 1827. 'Nomenclature for transport phenomena in electrolytic systems' on page 1836 (https://doi.org/10.1351/pac198153101827)

PAC, 1981,