Thermal Stability and Shape Evolution of Tetrahexahedral Au-Pd Core-Shell Nanoparticles with High-Index Facets

Nanosized metallic particles with high-index facets have exhibited excellent electrocatalytic activity and thus attracted intense interests over the past few years. Moreover, bimetallic particles with high-index facets could further enhance the catalytic activity by the synergy effects of high-index facets and electronic structures of the alloy. In this article, we employed atomistic simulations to investigate the thermal stability and shape evolution of tetrahexahedral Au Pd core shell nanoparticles respectively enclosed by {210) and (310) facets. The ground-state energy calculations indicated that the (210) faceted nanoparticles are more structurally stable than the (310) faceted ones. More importantly, it has been discovered that the former possess better thermal and shape stabilities than the latter. The Lindemann index was introduced to shed light on the melting mechanism, and the atomic distribution function was adopted to describe the diffusion tendency. For these two high-index terminated Au Pd bimetallic nanoparticles, the core and the shell exhibit different thermal evolution as they are heated to melting, though the melting generally proceeds from the shell into the core. Beyond the overall melting, Au atoms prefer to aggregate near the surface to favor the minimization of the total energy. These results are helpful for understanding the composition, shape, and thermodynamic properties of high-index faceted nanoparticles and therefore could be of great importance to the development of bimetallic core shell nanocatalysts with both high reactivity and excellent stability.