Author: ["Olga Lopez-Acevedo","Katarzyna A. Kacprzak","Jaakko Akola","Hannu Häkkinen"]
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Abstract
Finely dispersed nanometre-scale gold particles are known to catalyse several oxidation reactions in aerobic, ambient conditions. The catalytic activity has been explained by various complementary mechanisms, including support effects, particle-size-dependent metal–insulator transition, charging effects, frontier orbital interactions and geometric fluxionality. We show, by considering a series of robust and structurally well-characterized ligand-protected gold clusters with diameters between 1.2 and 2.4 nm, that electronic quantum size effects, particularly the magnitude of the so-called HOMO–LUMO energy gap, has a decisive role in binding oxygen to the nano-catalyst in an activated form. This can lead to the oxidation reaction 2CO + O2 → 2CO2 with low activation barriers. Binding of dioxygen is significant only for the smallest particles with a metal core diameter clearly below 2 nm. Our results suggest a potentially viable route to practical applications using ligand-protected gold clusters for green chemistry. Gold nanoparticles can catalyse oxidation reactions in remarkably mild conditions and have excited much interest in recent years. With experimental studies disagreeing over the size of the most active nanoparticles, density functional calculations have now shown that limiting the particle size to below two nanometres is crucial. Cite this article
Lopez-Acevedo, O., Kacprzak, K., Akola, J. et al. Quantum size effects in ambient CO oxidation catalysed by ligand-protected gold clusters. Nature Chem 2, 329–334 (2010). https://doi.org/10.1038/nchem.589 