Effect of Ionomer-to-Carbon Ratio on PEMFC Carbon Corrosion: An Electrochemical Study

This study investigates the effect of the ionomer-to-carbon (I/C) weight ratio in polymer electrolyte membrane fuel cell (PEMFC) cathode catalyst layers (CCLs) on carbon corrosion during high-potential accelerated stress tests (ASTs). Membrane electrode assemblies (MEAs) with I/C ratios of 0.5, 0.85, and 1.2 were analyzed using polarization curves, cyclic voltammetry, limiting current measurements, and electrochemical impedance spectroscopy. Impedance data analysis, based on distribution of relaxation times and transmission line modeling, showed that higher I/C ratios (0.85 and 1.2) exhibit superior beginning-of-life (BoL) performance due to lower ionic resistance in the CCL. However, the MEA with a lower I/C ratio (0.5) exhibited a performance improvement of up to 35% during initial AST cycles and enhanced carbon corrosion resistance. Compared to BoL, performance improved significantly due to a 28%–46% reduction in charge transfer resistance and a 91% reduction in ionic resistance. These findings emphasize the trade-off between BoL performance and long-term durability when determining the optimal I/C ratio. They also underscore the need for further investigation into how the I/C ratio influences CCL structure and electrochemistry. Optimizing the I/C ratio has the potential to substantially improve PEMFC electrode performance and durability, guiding the design of more resilient catalyst layers.