Gold Doping in PtCu3/HSAC Nanoparticles and Their Morphological, Structural, and Compositional Changes during Oxygen Reduction Reaction Electrochemical Cycling

Pt-based nanoparticles supported on high-surface-area carbon (HSAC) show very good properties as catalysts in polymer electrolyte membrane fuel cells (PEMFC). In many cases, however, the initial high activity of such catalysts rapidly drops as caused by various detrimental phenomena occurring in a typical electrochemical environment. In this work, a detailed study of a highly active system composed of PtCu3/HSAC nanoparticles with partially ordered structure and Pt skin with the addition of Au is performed. By using aberration-corrected scanning transmission electron microscopy, the effects of adding small amounts of gold compared to the nonmodified sample are followed through the different stages of an electrochemical cycling degradation protocol. Various morphological changes such as faceting, reshaping, and thickening of the Pt skin are investigated for both sets of samples on the atomic level. Interesting features such as well-defined shapes and surface defects are observed after degradation. However, the most important differences in terms of durability seem related to particle porosity. Finally, the experimental morphological observations are successfully reproduced by dealloying simulation with kinetic Monte Carlo modeling.