Towards accurate ex-situ determination of the BPP-GDL interfacial contact resistance

Apparently straightforward, accurate determination of the area specific resistance of the BPP-GDL interfacial contact (ICR) used in PEM-based fuel cells and electrolyzers remains a challenging task, mainly because uniform biasing current flow through the transverse sections of the measuring cell (MC) is required. In an attempt to improve the accuracy of the ICR determination, a finite element method (FEM)-assisted solution is proposed in the present work. To this end, a MC of cylindrical symmetry comprising two elongated electrodes, and a stack from two stainless steel BPP discs and a carbon paper GDL disc in-between was built; for access to voltage reading inside the MC, the opposing facets of the BPP discs were machined to a ribs-and-channels profile. We have shown that if equal currents are injected in this MC through six symmetrically placed contacts, with an accuracy better than 1% the voltage drop across the BPP-GDL interface does not depend on the voltage reading points location on the BPP channels bed, thus confirming that to a great extent the above requirement for uniform current is met. ICR values falling into the same range (tens of mΩcm −2 ) as those reported for similar BPP and GDL materials and clamping conditions were obtained.