Understanding the Morphology and Mass Transport Resistance of Mesoporous Carbon-supported PEMFC Based on Modeling Analysis

Mesoporous carbon supports mitigate Pt sulfonic poisoning through nanopore-confined Pt deposition, yet their morphological impacts on oxygen transport remain unclear. This study integrates carbon support morphology simulation with an enhanced agglomerate model to establish a mathematical framework elucidating pore evolution, Pt utilization, and oxygen transport in catalyst layers. Results demonstrate dominant local mass transport resistance governed by three factors: (1) active site density dictating oxygen flux; (2) ionomer film thickness defining shortest transport path; (3) ionomer-to-Pt surface area ratio modulating practical pathway length. At low ionomer-to-carbon (I/C) ratios, limited active sites elevate resistance (Factor 1 dominant). Higher I/C ratios improve the ionomer coverage but eventually thicken ionomer films, degrading transport (Factors 2–3 dominant). The results indicate that larger carbon particles result in a net increase in local transport resistance by reducing external surface area and increasing ionomer thickness. As the proportion of Pt situated in nanopores or the Pt mass fraction increases, elevated Pt density inside the nanopores exacerbates pore blockage. This leads to the increased transport resistance by reducing active sites and increasing ionomer thickness and surface area. Lower Pt loading linearly intensifies oxygen flux resistance. The model underscores the necessity to optimize support morphology, Pt distribution, and ionomer content to prevent pore blockage while balancing catalytic activity and transport efficiency. These insights provide a systematic approach for designing high-performance mesoporous carbon catalysts.