Abstract
Atomically precise thiolate protected Au nanoclusters Au38(SC2H4Ph)24 on CeO2 were used for in-situ (operando) extended X-ray absorption fine structure/diffuse reflectance infrared fourier transform spectroscopy and ex situ scanning transmission electron microscopy–high-angle annular dark-field imaging/X-ray photoelectron spectroscopy studies monitoring cluster structure changes induced by activation (ligand removal) and CO oxidation. Oxidative pretreatment at 150 °C “collapsed” the clusters’ ligand shell, oxidizing the hydrocarbon backbone, but the S remaining on Au acted as poison. Oxidation at 250 °C produced bare Au surfaces by removing S which migrated to the support (forming Au+-S), leading to highest activity. During reaction, structural changes occurred via CO-induced Au and O-induced S migration to the support. The results reveal the dynamics of nanocluster catalysts and the underlying cluster chemistry.
Highlights
Precise thiolate protected Au nanoclusters Au38(SC2H4Ph)[24] on CeO2 were used for in-situ extended X-ray absorption fine structure/diffuse reflectance infrared fourier transform spectroscopy and ex situ scanning transmission electron microscopy−high-angle annular dark-field imaging/X-ray photoelectron spectroscopy studies monitoring cluster structure changes induced by activation and CO oxidation
Thiolate-protected metal nanoclusters (Mn(SR)m) with well-defined structures offer creating atomically precise and catalytically a route toward active sites,[1−4] providing model systems for atomic level studies of catalytic properties.[3,5,6]. It is well-accepted that Au clusters supported by metal oxides exhibit excellent catalytic activity for oxidation[4,7−14] and hydrogenation,[15−17] especially when compared with larger Au nanoparticles
The initially well-defined Au cluster structure may change during pretreatment and reaction, which is affected by cluster size and the type of support material.[18−21] Previously, we have studied structural changes of
Summary
Sample preparations were performed by S.P. and C.G. EXAFS measurements were performed by N.B., V.T. and S.P.
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