Understanding the catalytic activity of gold nanoparticles through multi-scale simulations

We investigate how the chemical reactivity of gold nanoparticles depends on the cluster size and shape using a combination of simulation techniques at different length scales, enabling us to model at the atomic level the shapes of clusters in the size range relevant for catalysis. The detailed atomic configuration of a nanoparticle with a given number of atoms is calculated by first finding overall cluster shapes with low energy and approximately the right size, and then using Metropolis Monte Carlo simulations to identify the detailed atomic configuration. The equilibrium number of low-coordinated active sites is found, and their reactivities are extracted from models based on Density Functional Theory calculations. This enables us to determine the chemical activity of clusters in the same range of particle sizes that is accessible experimentally. The variation of reactivity with particle size is in excellent agreement with experiments, and we conclude that the experimentally observed trends are mostly explained by the high reactivity of under-coordinated corner atoms on the gold clusters. Other effects, such as the effect of the substrate, may influence the reactivities significantly, but the presence of under-coordinated atoms is sufficient to explain the overall trend.

By calculating the atomic-scale shape of gold nanoparticles, and thus the number of catalytically active sites, it is possible to calculate their reactivity. The size dependence of the reactivity is in excellent agreement with experiments, allowing the conclusion that the reactivity is dominated by low-coordinated corner-like atoms.Figure optionsDownload high-quality image (116 K)Download as PowerPoint slideHighlights
► A multi-scale simulation method predicting the catalytic activity of gold nanoparticles.
► The activity of the under-coordinated gold atoms can be calculated based on DFT.
► Quantitatively reproduce the trends in catalytic activity observed experimentally.
► The multi-scale simulation method is generally applicable to metallic nanoparticles.