Ab Initio Insights into the Formation Mechanisms of 55-Atom Pt-Based Core–Shell Nanoalloys

Platinum-based nanoalloys can yield unique properties due to synergistic effects derived from the combination of Pt with one or more transition-metal (TM) species, as well as from the chemical ordering within the particles such as the formation of core–shell PtTM structures. Although several studies have been reported, our atomistic understanding of the key physical and chemical descriptors that lead to the formation and stability of the core–shell structures are not completely understood. Here, we discuss such descriptors to understand the formation and stability of 11 platinum-based nanoalloys through ab initio density functional theory calculations employing 55-atom PtTM model systems. Studying several properties and using the Spearman correlation analysis, we found that the core–shell PtTM nanoalloys are energetically more stable if the surface region is populated by the chemical species with larger atomic radius and lower surface energy, which helps to reduce strain and forms stable structures. For nanoalloys of chemical species with large difference in the electronegativity, the energetic stability is enhanced by the Coulomb attraction between the cationic core and anionic surface derived from charge transfer, which increases the strain on the core and contributes to increase the segregation of large species to the surface region. Thus, the atomic radii, surface energies, and charge transfer play a crucial role in the formation and stability of core–shell PtTM nanoalloys.