3D Chemical Mapping of PEM Fuel Cell Cathodes by Scanning Transmission Soft X-ray SpectroTomography

Soft X-ray spectrotomography was applied for 3D chemical analysis of fuel cell cathodes at the nano scale. The goal was to obtain 3D maps of the components constituting the catalyst layer, and, in particular, to differentiate 3D networks of carbon support and ionomer. Using scanning transmission soft X-ray microscopy (STXM) with a rotating sample holder we produced a series of images at selected photon energies and different rotational angles of the sample. The rotational image stacks were tomographically reconstructed, while the X-ray absorption fingerprints at the C1s and F1s edges were used to generate 3D maps of the networks of carbon-support/catalyst and the fluorine-rich ionomer.