Recent experiments in oxidation catalysis indicate that bilayer gold nanostructures exhibit exceptional catalytic activity at ambient temperatures. Here we use molecular dynamics simulations to show that an unsupported bilayer gold nanocluster has a melting transition smeared out over a broad temperature range. The transition is characterized by an interplay between the intralayer and interlayer diffusion processes, and the transition temperature region ranges from about 300 to 1200 K. We suggest that surface thermal instabilities of partially melted bilayer gold nanoclusters result in their exceptional catalytic activity at ambient temperatures. For gold nanoclusters with more than two layers, the melting transition temperature range narrows, and the activity of the cluster decreases due to the suppression of surface fluctuations. These results systematically explain experimental observations showing that catalytic ability of gold nanoclusters decreases with size.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Electronic, Optical and Magnetic Materials
- Surfaces, Coatings and Films