Effect of Compression on Microstructure and Fluid Transport Properties on an Electrospun Gas Diffusion Layer for PEMFC from 3D High-Resolution Imaging

The impact of uniaxial compression of an electrospun Gas Diffusion Layer (eGDL) in the proton exchange membrane fuel cell (PEMFC) on microstructure and fluid transport properties (diffusion, tortuosity, permeability) is studied. An advanced high-resolution imaging method involving synchrotron X-ray tomography (XCT) and focus ion beam scanning electron microscopy (FIB-SEM) is employed. A comprehensive comparison between an eGDL and an MPL-free commercial GDL from Sigracet reveals that increased compression accentuates the local minimum porosity of the commercial GDL, due to the presence of binder and hydrophobic treatment. The effective diffusion coefficient of the commercial GDL is also more impacted than that of the eGDL. The resulting mass transport resistance of the commercial GDL increases by up to 11% with the compression rate, while it decreases by up to 30% for the eGDL. The limiting current density obtained in the cell for the eGDL rises by up to 65% with compression, reaching a value only 9% lower than that of the commercial GDL. High compression helps evacuate the liquid phase from the eGDL structure and subsequently reduces the mass transport resistance of the cell assembly.