Macroscopic Access Resistances Hinders the Measurement of Ion-Exchange-Membrane Performances for Electrodialysis Processes

Ion exchange membranes (IEMs) are widely used in various industrial sectors from batteries and energy harvesting to water treatment and are designed to show a high selectivity and a low electrical resistance. However, measuring their properties presents difficulties and can give rise to varying interpretations. This is particularly true for membranes prepared for reverse-electrodialysis (RED) applications. In this paper, the relation between membrane area and cell electrical resistance (and hence RED power density) is systematically investigated for a given commercial membrane (Nafion 115) in a standard lab-scale electrochemical cell. Our study case is RED, but the results can be extrapolated to other applications. The cell resistance is measured with respect to the membrane area and successfully modeled theoretically by introducing a macroscopic access resistance to the membrane. Resistance and produced power are then measured in a reverse-electrodialysis configuration. Based on this work, a few recommendations are formulated to perform scalable and meaningful measurements of membrane resistance and the associated performance like power density in the case of reverse electrodialysis.