Evaluation of Resistance Contributions from through-Plane Membrane Proton Transport, Electronic Components and Membrane-Electrode Interface in Fuel Cells

Proton exchange membrane fuel cells (PEMFCs) are receiving significant research attention for automotive, stationary and portable power applications. A major contributor to PEMFC inefficiency is resistance losses from the membrane, soft-goods (i.e., flow fields, gas diffusion medias), and interfaces between these components. Ascribing these losses to the individual components is a key challenge in evaluating and improving PEMFC performance. Of particular interest is measuring through plane membrane resistance, as unlike the other components this is highly variable with temperature and relative humidity. Though effective techniques have been developed for measuring in-plane membrane resistance through use of separate source and sense leads (four-point-probe measurements) these types of measurements are precluded for through-plane measurements due to membrane thinness (< 50 µm). In-plane membrane resistance measurements may correlate well with through-plane resistance for homogenous isotropic membranes, but have large errors for non-homogeneous membrane structures (e.g. extruded or supported membranes).

In this study, we developed a method to evaluate membrane resistance in the through-plane direction. We also evaluated the soft-good and contact resistances through both ex-situ and in-situ tests. The resistivity/conductivity of membranes with different structures were studied and compared in both through-plane and in-plane directions at various test conditions.