Novel Designs for 7-Layer Membrane Electrode Assembly in PEM Fuel Cells: A Systematic Investigation of Mass Transport and Charge Transfer Processes in PEM Fuel Cells

Abstract

During the last decades, the focus of PEM fuel cell development in automobile applications has been mostly dedicated to the optimization of the catalyst-coated membrane (CCM). Nevertheless, the optimum design of other components like the gas diffusion layer, or gas flow fields can directly influence the overall performance of the PEM fuel cell. The gas diffusion layer (GDL) itself plays a crucial role in the water balance in a PEM fuel cell. Besides, an optimized combination of GDLs and gas flow fields leads to the efficient distribution of reactants on catalyst layers. Our main goal for the development of the 7-layer membrane electrode assembly in PEM fuel cells is to reduce the corresponding thickness. This will both improve the efficiency of mass, electrical, and heat transport processes and reduce materials and energy consumption during production. Thus, it will contribute in two ways to support the commercialization of PEM fuel cells.Further intentions of our new GDL designs are, on one hand, optimizing the capillary pressure gradient for a smooth discharge of saturated water between the catalyst layer and gas flow fields. On the other hand, enhancing the gas transport to the catalysts layer by reducing diffusion length. These could be obtained by innovative engineering of microporous structures in GDLs. Thus, following beyond the previous investigation of our research group to enhance the capillary pressure gradient, and subsequently, mass transport, in this study the design of the microporous layer is purposely varied by applying different mono disperse polymer particles as pore former. In addition, to reduce the cell width in a disruptive manner, two innovative architectures have been investigated. The first one consists in eliminating the gas diffusion medium (GDM) and thus keeping only the newly-designed MPLs. Consequently, in comparison with a conventional GDL, the uncompressed material thickness is reduced from approximately 200 µm to around 40 µm. The second cell architecture is based on the integration of the refined gas flow fields directly at the back of the GDL which enables us to get rid of “large” rib/channel designs used in state-of-art bipolar plates.In this contribution, the effect of new-designed MPLs, as well as the mechanically machined GDL on both mass transport and the charge transfer processes have been evaluated and significant performance gains have been obtained. Additionally, the scale-up possibility from the single-cell design to short-stack PEM fuel cells will be discussed.This work from the “DOLPHIN” project has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking (now Clean Hydrogen Partnership) under Grant Agreement No 826204. This Joint Undertaking receives support from the European Union’s Horizon 2020 Research and Innovation program, Hydrogen Europe and Hydrogen Europe Research.