Chemical Fingerprint Associated with the Formation of Pt in the Membrane in PEM Fuel Cells

In this study, localized chemistry around Pt crystals formed in the membrane in an end-of-life (EOL) fuel cell catalyst coated membrane (CCM) was studied using near edge X-ray absorption spectra (NEXAFS) recorded with scanning transmission X-ray microscopy (STXM). X-ray Photoelectron spectroscopy (XPS) was applied to analyze the composition of the cathode catalyst powder used to prepare the CCMs. The XPS data indicated the presence of N-containing impurities within the catalyst powder with N 1s peak position consistent with a majority of NHx but also minority nitrate and nitrite environments. The region around the Pt particles in the membrane of EOL samples had N 1s near edge X-ray absorption spectra similar to those from the cathode catalyst and not from the membrane or the embedding epoxy. The results suggest the involvement of an unreduced Pt- N containing ligands -complex in the formation of Pt in the membrane.