Revealing in-plane movement of platinum in polymer electrolyte fuel cells after heavy-duty vehicle lifetime

Fuel cell heavy-duty vehicles (HDVs) require increased durability of oxygen-reduction-reaction electrocatalysts, making knowledge of realistic degradation mechanisms critical. Here identical-location micro-X-ray fluorescence spectroscopy was performed on membrane electrode assemblies. The results exposed heavy in-plane movement of electrocatalyst after HDV lifetime, suggesting that electrochemical Ostwald ripening may not be a local effect. Development of local loading hotspots and preferential movement of electrocatalyst away from cathode catalyst layer cracks was observed. The heterogeneous degradation exhibited by a modified cathode gas diffusion layer membrane electrode assembly after HDV lifetime was successfully quantified by the identical-location approach. Further synchrotron micro-X-ray diffraction and micro-X-ray fluorescence experiments were performed to obtain the currently unknown correlation between electrocatalyst nanoparticle size increase and loading change. A direct correlation was discovered which developed only after HDV lifetime. The work provides a route to engineer immediate system-level mitigation strategies and to develop structured cathode catalyst layers with durable electrocatalysts.

Automated summary

Fuel cell heavy-duty vehicles (HDVs) require more durable oxygen-reduction-reaction electrocatalysts, and understanding the realistic degradation mechanisms is crucial. The study investigated the movement and degradation of electrocatalysts in membrane electrode assemblies using micro-X-ray fluorescence spectroscopy. It was found that the electrocatalyst exhibited heavy in-plane movement and preferential movement away from cracks in the cathode catalyst layer. By performing further experiments, the correlation between the increase in nanoparticle size of the electrocatalyst and loading change was discovered. This research provides insights for developing mitigation strategies and durable electrocatalysts in structured cathode catalyst layers.