Issues regarding bipolar plate-gas diffusion layer interfacial contact resistance determination

The interfacial contact resistance (ICRBPP-GDL) between the bipolar plates (BPPs) and gas diffusion layers (GDLs) plays a major role in proton exchange membrane-fuel cells (PEMFCs) efficiency. Accordingly, materials selection based on ex-situ ICRBPP-GDL determination is a useful tool, provided accurate through-plane resistance measurements are ensured; in this sense, an experimental study was conducted. To this end, two square-shaped samples of equal areas, one from stainless steel (a low cost BPP material), and one from carbon paper (a widely used GDL material) were placed (both separately, and stacked) between two planar Cu electrodes, and the through-plane resistance of the as-formed measuring cell was determined at various applied clamping pressures (p). It was found that although falling into the same order of magnitude (tens of mΩ cm2), the results extracted from these measurements as ICRBPP-GDL (p) are affected by the non-uniformity of the current flow through the measuring cell, and also by the position of the voltage pick-up contacts. It was concluded that if reasonably uniform path is ensured for the biasing current by splitting this into four equal currents, and if central points are used for voltage pick-up, realistic results are expected.