Summary The commercialization of polymer electrolyte membrane fuel cells has been hindered by durability problems caused by defects in the manufacturing process. We demonstrate for the first time a non‐destructive, non‐contact method that uses optical microscopy and image analysis to identify defects that may lead to failure in catalyst‐coated membranes (CCMs) of polymer electrolyte membrane fuel cells. This method is applied to 2 commercial CCMs produced by the decal transfer technique. Defects in the catalyst layer (CL) at the beginning‐of‐life (BOL) are characterized in terms of their initial size and shape, and their propagation is tracked as the CCMs are aged in a non‐reactive environment. The defected area in one of the commercial CCMs increases from approximately 2.4% of the total CL area at BOL to 10.5% by end‐of‐life (EOL). BOL defects in the CL are found to propagate faster in the CCMs stored for 2 years under atmospheric conditions compared with freshly manufactured CCMs with narrow CL defects. Image analysis of another commercial CCM shows the presence of pores with diameters between 5 and 25 μm that comprise 52% of the total pore area in the CL. Other defects such as scratches and missing/empty catalyst areas are identified and characterized, providing a framework for quality control applications. Finally, the effect of defects on fuel cell performance is characterized by measurement of the open‐circuit voltage (OCV). These experiments show that CCMs with a large number of cracks in the CL exhibit a voltage loss of 2.55 mV/hr, whereas CCMs with thin/missing/empty CL defects show a loss of 1.12 mV/hr.
Catalyst layer defects and irregularities in catalyst-coated membrane (CCM) electrodes affect the lifetime of polymer electrolyte membrane fuel cells (PEMFCs) during their operation. Thus, catalyst layer defects are important concerns for fuel cell manufacturers and prompt the development of quality control systems with the aim of fabricating defect-free electrodes. Consequently, the objective of this study is to gain a fundamental understanding of the morphological changes of real catalyst layer defects that have developed during CCM production. In this paper, missing catalyst layer defects (MCLD) formed during the decal transfer process are investigated through a nondestructive method using reflected light microscopy. The geometric features of the defects are quantified, and their growth is measured at regular time intervals from beginning-of-life (BOL) to end-of-life (EOL) until the OCV has dropped by 20% of its initial value as per a DOE-designed protocol. Overall, two types of degradation are observed: surface degradation caused by catalyst erosion and crack degradation caused by membrane mechanical deformation. Furthermore, catalyst layer defects formed during the decal transfer process were found to exhibit a higher growth rate at middle-of-life (MOL-1) and stabilize by EOL. This type of study will provide manufacturers with baseline information to allow them to select and reject CCMs, ultimately increasing the lifetime of fuel cell stacks.
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