Résumé
This experiment aims at employing, for the first time, operando X-ray (total) scattering to investigate two crit-ical processes occurring on Pt electrocatalyst at the cathode of a high temperature proton exchange membrane fuel cell (HT-PEMFC): (i) Pt surface oxidation and (ii) Pt poisoning by phosphoric acid electrolyte. The pro-posal relies on the sensitivity of the Pt microstructure to these two processes, as recently demonstrated by our consortium for low temperature PEMFCs (LT-PEMFCs). These observations, carried over a range of various electrode and membrane materials, will allow us to (i) establish the critical cathode potentials for Pt poisoning and oxidation and (ii) correlate them with the electrode and electrolyte properties, thus identifying optimal electrode designs.