Transport phenomena within gas diffusion layers (GDLs) of of proton exchange membrane fuel cells (PEMFCs) are crucially important for an optimum PEM fuel cell performance. The microstructure properties of the GDLs, such as porosity, tortuosity and pore size distribution govern the transport of fluid, heat and charge. Additionally, PEM fuel cells are assembled under high compression pressure to minimize the contact resistance between components. The compression significantly alters the microstructure of the GDLs, and affects the cell performance substantially by blocking the pathways of liquid and gas species to and from the catalyst layer reaction sites. This study gives detailed understanding on the effect of compression on a GDL microstructure using high resolution X-ray Computed Tomography. Porosity distributions were shown when the GDL is compressed. A significant GDL penetration into the gas channel was observed at high compression pressures.

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