Mitigation and diagnosis of pin-hole formation in polymer electrolyte membrane fuel cells

Abstract

Membrane electrode assemblies (MEAs) are prone to process-induced pin-holes during the hot-press lamination step often required for gas diffusion electrode (GDE) based MEAs. Membrane pin-holes can result in the crossover of hydrogen (H2) fuel, which inevitably leads to fatal damage of the MEA and fuel cell failure. In this work, we implement a calendering technique to flatten stray fibers within the gas diffusion media, thereby mitigating pin-hole formation in the hot-pressed MEAs. We have investigated the influence of calendering on the long-term durability for several types of gas diffusion electrodes (GDEs) using a combined chemical and mechanical accelerated stress test (AST). The calendered MEAs demonstrate an average AST lifetime improvement of 77% relative to the as-fabricated MEAs. In addition, voltage transients measured throughout the AST were utilized to determine the onset of pin-hole formation and subsequent cell failure. Voltage transients have the advantage of application to fuel cell stacks in lieu of ubiquitous single cell H2 crossover measurements. The application of both voltage transients and calendering pre-treatment is of broad interest to those seeking improvements to the MEA process quality, since the use of GDEs in MEAs is universal across electrochemical energy conversion applications such as CO2 and water electrolysis.