Failure Analysis and Defects Characterization of Polymer Electrolyte Membrane Fuel Cells after Relative Humidity Cycling

Commercial catalyst coated membrane (CCM) was tested under a relative humidity (RH) cycling accelerated stress test (AST). The morphology around the failed regions, identified by the bubble jig test, were examined by scanning electron microscopy (SEM), scanning transmission electron microscopy-energy dispersive spectroscopy (STEM-EDS), and X-ray computed tomography (XCT) and compared with beginning of life (BOL) sample. The SEM images showed the defects in forms of catalyst layer (CL) and membrane cracks, delamination, and bulging along with CL thickness alterations. The XCT scans confirmed the presence of circular and volcano-shape defects protruded throughout the CCM, as well as MPL irregularities. Defects were correlated to the morphology of the microporous layer (MPL), suggesting that MPL structure may affect the degradation of CCMs. The STEM-EDS microstructural evaluations and analysis revealed changes in the CL porosity with respect to the BOL, confirming the thickness changes and defect formation observed in SEM and XCT.