Functional Materials for Energy
Thiolate Ligands as a Double-Edged Sword for Catalysis by Thilated Gold NanoclustersMay 19, 2014
Figure Caption: CO oxidation mechanism over intact and partially de-thiolated Au25(SR)18/CeO2-rod
Scientific Achievement: Thiolate ligands in gold cluster compounds are revealed to be a ‘double-edged sword’: ligands protect and stabilize the cluster but block sites responsible for catalytic activity.
Significance and Impact: Ligated gold molecules provide a route to highly uniform catalysts and understanding the role of ligands in protected metal clusters is a prerequisite for the rational design of efficient metal catalysts.
Details: The effect of thiolate ligands on the catalysis of Au25(SR)18/CeO2-rod has been probed by CO oxidation via reaction test, in situ IR, X-ray absorption (EXAFS and XANES) spectroscopy, isotopic labelling, and DFT calculation. It was concluded that the thiolate ligands act as a double-edged sword for the Au25 nanoclusters for CO oxidation in the gas phase. Specifically, the thiolate ligands maintain the structural integrity of Au25(SR)18, but disable all Au sites from adsorbing CO and thus the intact catalyst is not active for CO oxidation. Partial removal of thiolate ligands, starting from the interface between Au25(SR)18 and CeO2 at treatment temperatures of 423 K and above, is required for CO activation and thus the onset of low temperature CO oxidation on the Au25(SR)18/CeO2-rod catalyst. The removal of thiolate ligands on Au25(SR)18/CeO2-rod results in three types of Au sites: Aud+ (0
Wu, Z.; Jiang, D.; Mann, A.; Mullins, D.; Qiao, Z.-A.; Allard, L.; Zeng, C.; Jin, R.; Overbury, S., “Thiolate Ligands as a Double-Edged Sword for CO Oxidation on CeO2-Supported Au25(SCH2CH2Ph)18 Nanoclusters”. J. Am. Chem. Soc. 2014, 136(16), 6111