Material, process parameter, and defect investigation for scalable fabrication of catalyst-coated membranes for proton-exchange membrane fuel cells

Proton exchange membrane fuel cells (PEMFCs) are promising zero-emission power sources for electric vehicles and stationary power systems. The efficiency and durability of PEMFCs are significantly influenced by the anode and cathode catalyst layer (CL), which are bonded onto a membrane to form a catalyst-coated membrane (CCM). These layers facilitate the essential electrochemical reactions required for the power generation. This Ph.D. thesis focuses on enhancing the scalable fabrication of CCMs by concentrating on the creation of the CLs through direct film coating methods (DFCMs). Additionally, it investigates the impacts of various process parameters and defects on the quality of these layers and overall PEMFC performance. The research aims to bridge the gap between laboratory studies and industrial applications by examining how material properties, coating techniques, and process parameters affect the CL's structural and functional characteristics. Initial work involves selecting catalyst ink materials and establishing robust fabrication and analysis methodologies. Techniques such as sonication, high-shear mixing, Mayer-rod, and Doctor-blade coating are utilized to optimize ink formulations and coating processes at the lab-scale. Comparative studies between lab-scale and large-scale coating methods, including Slot-die and Micro-gravure coating, provide insights into scaling up CL production. The thesis explores the effects of coating speed, drying methods, and ink formulations on catalyst loading and PEMFC efficiency. By refining these parameters, the research contributes to improving the consistency and performance of large-scale CL fabrication. Further investigations address common fabrication defects, such as missing CL areas and gas bubble entrapment within the membrane, and their detrimental effects on PEMFC performance and durability. Advanced analytical techniques, including X-ray imaging, are employed to study material uniformity and localized degradation phenomena, particularly during start-up and shut-down cycling, thereby highlighting the benefits of X-ray imaging for PEMFC analysis. The thesis findings contribute to the advancement of manufacturing standards for PEMFCs, aimed at improving their efficiency, reliability, and commercial viability. Overall, this research advances PEMFC technology by improving our understanding of material and process parameters in CL fabrication, thereby facilitating its broader adoption in various applications.