STXM Characterization of PEM Fuel Cell Catalyst Layers

The synchrotron based scanning transmission soft X-ray microscopy (STXM) utilizing near edge X-ray absorption fine structure (NEXAFS) is a novel technique for characterization of membrane electrode assembly (MEA) components in proton exchange membrane fuel cells (PEMFC). Component maps for carbon support, Pt and ionomer in the cathode catalyst layer and perfluorosulphonic acid (PFSA) membrane including the reinforced layer have been obtained from full C 1s multi-energy image sequences and maps from images at four energies in the C 1s and F 1s regions. The ability of this technique to distinguish both structural and chemical differences in cathode catalyst layers from two significantly different designs has been demonstrated. The ionomer distribution in the cathode catalyst layer of an advanced catalyst coated membrane (CCM) structure is compared to that of the cathode in a gas diffusion electrode (GDE).