Salt concentration polarization of liquid electrolytes and determination of transport properties of cations, anions, ion pairs and ion triples

Abstract

Specifically blocking of cations or anions in an electrochemical polarization experiment is a standard procedure to determine transport numbers. This is non-trivial in the case that internal interaction (ion pairs, ion triples etc.) have to be taken account of. Besides the trivial concentration redistribution owing to mass action laws, it is the dynamics that is affected in a more complex way. The steady state behavior of such a polarization is calculated using the concept of Conservative Ensembles. By the same procedure also the relaxation time of the galvanostatic transient is addressed. Finally it is shown how the individual transport parameters of cations, anions, ion pairs and ion triples can be obtained by a combination of polarization, impedance spectroscopy and cationic as well as anionic tracer (or PFG-NMR) experiments.