https://doi.org/10.1351/goldbook.M03921
The difference between the current that is actually obtained, at any particular value of the potential of the
indicator
or working electrode
, for the reduction or oxidation
of an ionic electroactive substance
and the current that would be obtained, at the same potential, if there were no transport of that substance due to the electric field between the electrodes. The sign convention regarding current is such that the migration
current is negative for the reduction of a cation
or for the oxidation
of an anion
, and positive for the oxidation
of a cation
or the reduction of an anion
. Hence the migration
current may tend to either increase or decrease the total current observed. In any event the migration
current approaches zero as the transport number
of the electroactive substance
is decreased by increasing the concentration of the supporting electrolyte
, and hence the conductivity