Theoretical insights into the thermal behaviors and coalescence of truncated octahedral Au nanoparticles

Abstract

Truncated octahedral Au nanoparticles (NPs) dispersed on Ti-containing supports has been demonstrated as a promising catalyst for the propylene epoxidation with H2 and O2, while the catalytic stability for the industrial application is still challenging. Herein, thermodynamics analysis and molecular dynamics calculations are employed to address the thermal behaviors and coalescence of truncated octahedral Au NPs. The melting temperature of Au NPs is found to decrease with the decreasing particle size, and the melting initiates from the outermost edge and (100) atoms with lower coordination numbers followed by the (111) atoms and proceeds inwards. The coalescence of two Au NPs deforms smaller sized Au NP while remains the larger sized one at low temperatures, but the two nanoparticles melt into a fully mixed spherical one at high temperatures. Moreover, the (111) facet is more facile for the coalescence than other exposed facets on Au NPs.