Résumé
The long-term stability of Pt catalysts is critical to the reliability of proton exchange membrane fuel cells (PEMFCs), and receives constant attention. However, the current knowledge of Pt oxidation is restricted to unrealistic PEMFC cathode environment or operation, which questions its practical relevance.Herein, Pt oxidation is investigated directly in a PEMFC with stroboscopic operando high energy X-ray scattering. The critical potential for the Pt-O dipole place-exchange mechanism is observed far below the previously reported value, and most importantly, below the open-circuit potential of PEMFC cathode. Such early oxidation is shown to control PEMFC performance and its role on Pt transient dissolution is veri ed by electrochemical on-line inductively coupled plasma mass spectrometry. By further demonstrating and resolving the limitations of currently employed accelerated stress test protocols in the light of place-exchange time constants, this new paradigm of Pt oxidation paves the way to new mitigation strategies against PEMFC degradation