Electrical and thermal contact resistance of porous fuel cell electrodes

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Mercedes-Benz Canada-Fuel Cell Division (MBC) is engaged in the production of polymer electrolyte membrane fuel cell (PEMFC) stacks for zero emission road vehicles. The operation of PEMFC stacks depends critically on the membrane-electrode assembly (MEA), a multilayered component at the core of a cell that facilitates several transport processes and the electrochemical energy conversion that generates electrical power. The interfaces between the porous MEA layers have a significant impact on the effectiveness of the transport processes and, in turn, on the performance, reliability and durability of an automotive fuel cell stack. This research builds on a previous Engage project to determine electrical and thermal contact resistance. The study focuses on the interface between two specific components of the MEA: the catalyst layer and the micro-porous layer. The methodology involves (i) characterization of the surface roughness and morphology of the porous fuel cell materials using laser scanning microscopy; (ii) computational reconstruction of the contacting porous media; (iii) contact mechanics modelling of the interface; and (iii) prediction of effective interfacial transport properties using pore-scale simulations. This research will contribute toward the long term goals of quantifying the impact of manufacturing and assembly tolerances on interfacial transport in production MEAs. The study will allow determination of electrical and thermal contact resistance as a function of compressive pressure; and examination of the impact of defects such as holes and cracks.