In-situ investigation of crack formation during drying of catalyst layers for polymer electrolyte membrane (PEM) fuel cells and electrolyzer

The formation of cracks in catalyst layers for polymer electrolyte membrane fuel cells (PEMFC) and electrolyzers (PEMWE) is influenced by various parameters. The impact of these cracks on the device performance remains to be understood. Solvent mixtures used in ink production and the processing of catalyst-coated membranes (CCM), particularly in the drying step, can affect the development of cracks in the catalyst layers. This study presents a novel in-situ investigation of crack formation during an industrially relevant and scalable drying process for catalyst layers. In this regard, locally resolved film temperature and optical crack analysis were conducted simultaneously and in-situ during drying. Cracking is detected when the film consolidates, indicated by a temperature increase and the change in optical layer appearance. Different crack patterns for catalyst inks depending on the initial solvent composition are found and analyzed. Higher 1-propanol content in catalyst inks exhibits faster drying behavior under identical convective drying conditions and more pronounced crack formation, indicated by higher total crack area and larger crack morphologies. The study investigates crack formation in-situ during the drying of catalyst layers for PEM fuel cells and electrolyzers using different camera systems. The transition from constant-rate to falling-rate drying is identified as the critical point for crack initiation. Theoretical considerations on selective drying complement the experimental findings on the drying and cracking behavior of different ink formulations.