Secondary Electron Hyperspectral Imaging (SEHI) in FIB - SEM for Proton Exchange Membrane Fuel Cells Technology.

The performance of proton exchange membrane (PEM) fuel cells critically depends on the microstructure and chemistry of their constituent materials, particularly the catalyst layer (CL), carbon black (CB), ionomer films, and reinforced membranes. However, the highly heterogeneous and nanoscale nature of these components presents significant challenges for existing characterization techniques. This study explores the application of Secondary Electron Hyperspectral Imaging (SEHI) in focused ion beam-scanning electron microscopy (FIB-SEM) to address these limitations. SEHI uniquely integrates chemical sensitivity, surface specificity, and nanoscale spatial resolution, enabling detailed insights into key functional materials. Carbon black analysis revealed the spatial distribution of graphitised regions and surface functional groups, such as CO bonding, which are critical for optimizing electron transport and catalyst stability. For ionomer films and membranes, SEHI identified and mapped chemical differences between the ionomer matrix and its polybenzimidazole (PBI) reinforcement, distinguishing nitrogen species and surface functionalities. This capability facilitates a deeper understanding of how membrane composition and structure influence conductivity and durability. The results demonstrate SEHI's potential as a transformative tool for the nanoscale characterization of PEM fuel cell components, providing critical insights for the design and optimization of high-performance, durable fuel cells.