Fuel Cell Membrane Durability Implications of Locally Absent Microporous Layer

Although modern reinforced fuel cell membranes are designed for high durability, membrane degradation can incidentally be accelerated by its interaction with manufacturing related physical non-uniformities in other fuel cell subcomponents. It is therefore important to identify and understand the implications of these non-uniformities in order to improve quality control for fuel cell manufacturing. The present work investigates the chemo-mechanical membrane durability impacts of discrete sites of missing microporous layer (MPL) with controlled dimensions and locations as the target non-uniformity. Accelerated stress testing is utilized to vividly simulate stresses, with advanced failure monitoring via in-situ electrochemical diagnostics and four-dimensional X-ray computed tomography. Progressive local membrane deformation and thinning driven by exposed protruding carbon fibers underneath the missing MPL is discovered to cause critical electrode shorting failure. This exclusively occurs under flow plate lands, and is more severe with increasing missing MPL dimensions. Catalyst layer cracks are formed at missing MPL sites under flow channels, but with marginal impact on membrane durability. The missing MPL sites also have no evident impact on chemical membrane degradation. In conclusion, missing MPL is deemed as a potential risk to long-term membrane durability due to mechanical stress concentration, and should be avoided during fabrication.