This seventh talk in the series provided insights into our collaboration activities, specifically imaging of catalyst layers.
This study establishes quantitative correlations between catalyst layer (CL) microstructure, electrochemical performance, and degradation in proton exchange membrane fuel cells (PEMFCs) as a function of ionomer-to-carbon (I/C) weight ratio and relative humidity (RH). Conventional cathode catalyst layers were analyzed using high-resolution SEM, epoxy-free TEM, and STEM-EDS mapping, combined with automated deep-learning and Python-based image quantification. Structural descriptors—including CL thickness, porosity, ionomer coverage, connectivity, and platinum (Pt) particle size and migration to the membrane —were quantified and correlated with in-situ performance and accelerated stress test data. Increasing I/C ratio enhanced ionomer connectivity and proton transport under dry conditions but also promoted Pt dissolution, migration, and particle growth, especially under humid operation. High RH amplified Pt ion mobility and Pt band formation in the membrane (PITM), leading to significant electrochemically active surface area (ECSA) loss. Principal component analysis (PCA) revealed two competing degradation modes: catalyst transport–driven degradation governed by ionomer connectivity and humidity, and ionomer-related structural densification dominating under dry conditions. The findings highlight a critical trade-off—enhanced ionomer connectivity improves short-term performance yet accelerates long-term degradation. This data-driven quantitative microscopy framework provides mechanistic insight and practical guidance for optimizing CL architecture and humidity management to achieve durable, high-performance PEMFC electrodes.
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