An identical-location transmission electron microscopy study on the degradation of Pt/C nanoparticles under oxidizing, reducing and neutral atmosphere

This study shows that the predominant degradation mechanism of Pt/Vulcan XC72 electrocatalysts strongly depends on the nature of the gas atmosphere and of the upper potential limit used in accelerated stress tests (ASTs). The morphological changes of Pt/Vulcan XC72 nanoparticles were studied by identical location transmission electron microscopy (IL-TEM), following accelerated stress tests in different potential ranges and under various gas atmospheres. X-ray photoelectron spectroscopy was used to probe changes in carbon surface chemistry. Whereas minor changes were detected under neutral atmosphere (Ar) and low potential limit conditions (0.05 < E < 0.50 V vs. RHE), the migration/aggregation of Pt nanocrystallites was strongly accelerated in the presence of a reducing atmosphere, such as CO. Carbon corrosion and Pt nanoparticle detachment were more frequently observed under oxidizing atmosphere (O2). With an increase of the upper potential limit to 1.23 V vs. RHE, the trends observed previously were maintained but 3D Ostwald ripening strongly overlapped with the three other degradation mechanisms, precluding any identification of the dominant mechanism.