In-Depth Analysis of the Impact of Ionomer Content on PEMFC Degradation By Combining Electrochemical Characterization Techniques and Transmission Line Modeling

This study analyzes the influence of the ionomer-to-carbon ratio (I/C) in cathode catalyst layers (CCL) on carbon corrosion behavior during high-potential cycling accelerated stress tests (ASTs). Membrane electrode assembly (MEA) samples with varying I/C ratios (0.5/0.85/1.2) were evaluated using polarization curve measurements and electrochemical impedance spectroscopy (EIS) under H 2 /air conditions. Analysis through the distribution of relaxation times (DRT) and equivalent circuit modeling revealed that the MEAs with a high I/C ratio (1.2) and a medium I/C ratio (0.85) exhibited the highest beginning of life (BoL) performance, attributed to their lower ionic resistances. Conversely, the MEA with a low I/C ratio (0.5) showed significant improvement during initial AST cycles and superior carbon degradation resistance, despite poor BoL performance. This study highlights the need for further investigation to fully understand the impact of the I/C ratio on electrode structure and carbon corrosion behavior. Furthermore, the combined results suggest that optimizing the I/C ratio could enhance the durability of PEMFC electrodes.