Monitoring the Fate of Zn in the Cu/ZnO/ZrO Catalyst During CO-to-Methanol Synthesis at High Conversions by Operando Spectroscopy.

In the frame of developing a sustainable chemical industry, heterogeneously catalyzed CO hydrogenation to methanol has attracted considerable interest. However, the Cu-Zn based catalyst system employed in this process is very dynamic, especially in the presence of the products methanol and water. Deactivation needs to be prevented, but its origin and mechanism are hardly investigated at high conversion where product condensation is possible.

Directing Intrinsic Chirality in Gold Nanoclusters: Preferential Formation of Stable Enantiopure Clusters in High Yield and Experimentally Unveiling the "Super" Chirality of Au.

Chiral gold nanoclusters offer significant potential for exploring chirality at a fundamental level and for exploiting their applications in sensing and catalysis. However, their widespread use is impeded by low yields in synthesis, tedious separation procedures of their enantiomeric forms, and limited thermal stability. In this study, we investigated the direct synthesis of enantiopure chiral nanoclusters using the chiral ligand 2-MeBuSH in the fabrication of Au, Au, and Au nanoclusters.

Structural evolution after oxidative pretreatment and CO oxidation of Au nanoclusters with different ligand shell composition: a view on the Au core.

The reactivity of supported monolayer protected Au nanoclusters is directly affected by their structural dynamics under pretreatment and reaction conditions. The effect of different types of ligands of Au clusters supported on CeO on their core structure evolution, under oxidative pretreatment and CO oxidation reaction, was investigated. X-ray absorption and X-ray photoelectron spectroscopy studies revealed that the clusters evolve to a similar core structure above 250 °C in all the cases, indicating the active role of the ligand-support interaction in the reaction.

CeO Supported Gold Nanocluster Catalysts for CO Oxidation: Surface Evolution Influenced by the Ligand Shell.

Monolayer protected Au nanocluster catalysts are known to undergo structural changes during catalytic reactions, including dissociation and migration of ligands onto the support, which strongly affects their activity and stability. To better understand how the nature of ligands influences the catalytic activity of such catalysts, three types of ceria supported Au nanoclusters with different kinds of ligands (thiolates, phosphines and a mixture thereof) have been studied, employing CO oxidation as model reaction. The thiolate-protected Au/CeO showed significantly higher CO conversion after activation at 250 °C than the cluster catalysts possessing phosphine ligands.

Selective ligand exchange synthesis of Au(2-PET) from Au(SG).

Replacement of protecting ligands of gold nanoclusters by ligand exchange has become an established post-synthetic tool for selectively modifying the nanoclusters' properties. Several Au nanoclusters are known to additionally undergo size transformations upon ligand exchange, enabling access to cluster structures that are difficult to obtain by direct synthesis. This work reports on the selective size transformation of Au(SG) (SG: glutathione) nanoclusters to Au(2-PET) (2-PET: 2-phenylethanethiol) nanoclusters through a two-phase ligand exchange process at room temperature.

Dynamics of Pd Dopant Atoms inside Au Nanoclusters during Catalytic CO Oxidation.

Doping gold nanoclusters with palladium has been reported to increase their catalytic activity and stability. PdAu nanoclusters, with the Pd dopant atom located at the center of the Au cluster core, were supported on titania and applied in catalytic CO oxidation, showing significantly higher activity than supported monometallic Au nanoclusters. After pretreatment, DRIFTS spectroscopy detected CO adsorbed on Pd during CO oxidation, indicating migration of the Pd dopant atom from the Au cluster core to the cluster surface.

The Dynamic Structure of Au(SR) Nanoclusters Supported on CeO upon Pretreatment and CO Oxidation.

Atomically precise thiolate protected Au nanoclusters Au(SCHPh) on CeO 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.

Ligand engineering of immobilized nanoclusters on surfaces: ligand exchange reactions with supported Au(PPh)Br.

The properties of gold nanoclusters, apart from being size-dependent, are strongly related to the nature of the protecting ligand. Ligand exchange on Au nanoclusters has been proven to be a powerful tool for tuning their properties, but has so far been limited to dissolved clusters in solution. By supporting the clusters previously functionalized in solution, it is uncertain that the functionality is still accessible once the cluster is on the surface.

Ligand Migration from Cluster to Support: A Crucial Factor for Catalysis by Thiolate-protected Gold Clusters.

Thiolate protected metal clusters are valuable precursors for the design of tailored nanosized catalysts. Their performance can be tuned precisely at atomic level, e. g.