Surface Stability of Platinum Nanoparticles Surrounded by High-Index Facets

We have investigated the thermal stability of surface structures of tetrahexahedral platinum nanoparticles surrounded by high-index facets such as (730), (210), (310), and (520) by molecular dynamic simulation. The instantaneous atomic configurations, mean-squared displacement, radical distribution function, and average energy per atom are studied. At the lower temperature range, that is, 0∼860 K, both surface atoms and interior atoms oscillate around their equilibrium positions slightly and the high-index surface steps at which chemical reactions usually take place are maintained regularly. If the temperature is raised above 860 K, surface diffusion becomes dramatic and those surface steps disappear, though the general shape of the nanoparticles is still retained to a high temperature of 1100 K or so. Based on this study, the improved catalysis of Pt nanoparticles can be maintained only at temperatures lower than 860 K.