Studying Crack Formation in Catalyst Layer Films for Proton Exchange Membrane Fuel Cells

The performance and durability of proton exchange membrane fuel cells (PEMFCs) can be affected by cracks formed in catalyst layers (CLs). While previous research has shown that CLs prepared with pre-commercial high oxygen permeability ionomer (HOPI) are more efficient and durable, they can lead to significantly more cracking features than CLs prepared with traditional perfluorosulfonic acid (PFSA) ionomer. Therefore, it is important to reduce cracking to further improve cathode performance, durability, and film quality. With this goal in mind, we analyzed ink drying and crack formation during the wet-film coating process via imaging with an optical microscope fixed above a film applicator. Transient quantitative crack growth studies were performed to evaluate the dynamic nature of the process. Alongside that, the crack density of post-coating films was quantified at higher resolutions using a compound microscope. Ink composition, Pt-based catalysts and relative humidity of drying environment were varied in order to understand which combinations resulted in fewer cracks. This material is based upon work supported by the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy (EERE) under the Fuel Cell Technologies Office, Award Number DE-EE0008822.