Insights into the Ionomer Distribution through Elemental Mapping of Model Catalysts Mixed with Nafion

Cross-sections of morphology-controlled catalysts mixed with ionomer are analyzed with energy-dispersive X-ray spectroscopy. The elemental mappings provide information about the behavior of the ionomer on the nanoscale, including the penetration depth of the ionomer into small mesopores. Furthermore, the suitability of metal ion exchange for tracking the ionomer distribution is validated by post-impregnation with cesium. Ultimately, this work lays the foundation for a meaningful characterization of the ionomer distribution in catalyst layers of proton exchange membrane fuel cells.