Realistic Fuel Cell Catalyst Degradation via Automated Identical Location SEM-PSD Analysis with the GDE Half-Cell Setup

A realistic evaluation of electrocatalyst stability requires experimental setups that accurately reproduce the coupled chemical and transport environments of membrane-electrode assemblies. Conventional GDE half-cells, however, are typically operated without a proton-exchange membrane, exposing the catalyst layer directly to liquid electrolytes and intensifying dissolution-migration-redeposition dynamics. Here, we examine how the presence of a membrane alters degradation in PtCo/C catalyst layers and establish a quantitative workflow for tracking nanoparticle evolution under realistic conditions. Particle-size distributions (PSDs) are extracted directly from low-kV identical-location SEM (IL-SEM) images of intact, micrometer-thick porous catalyst layers and validated against IL-TEM for surface-accessible particles. Automated segmentation enables robust, high-throughput analysis across large datasets. Applying this framework to accelerated stress tests reveals that membrane-free GDEs undergo pronounced coarsening driven by severe Pt dissolution and redeposition under direct acid exposure, whereas membrane-protected electrodes constrain transport pathways and therefore exhibit more moderate, representative degradation behaviour. These findings underscore the indispensable role of the membrane for realistic half-cell durability studies and demonstrate that automated IL-SEM-based PSD analysis provides a powerful framework for linking morphological evolution to electrochemical performance in complex, three-dimensional porous electrocatalyst systems.