Morphology Effect of Ceria Supports on Gold Nanocluster Catalyzed CO Oxidation

Interfacial perimeter is generally viewed as the catalytically active sites for a number of chemical reactions over the oxide-supported nanogold catalysts. Here, the well-defined CeO2 of nanocube, nanorod and nanopolyhedra are chosen to accommodate the atomically precise clusters (e.g. Au25(PET)18) to give different Au cluster-CeO2 interfaces. TEM images show the Au particles of ~ 1.3 nm are uniformly anchored on the ceria surface after the 120 oC annealing in air, which can rule out the size hierarchy of nanogold in the CO oxidation investigations. The gold nanoclusters are only immobilized on the CeO2(200) facet in Au25/CeO2-C, while they are selectively loaded on the CeO2(002) and (111) in the Au25/CeO2-R and Au25/CeO2-P catalysts. X-ray photoelectron spectroscopy (XPS) and in-situ infrared CO adsorption experiments clearly demonstrate the gold species in the Au25/CeO2 samples are similar and partial charged (Auδ+, where 0<δ<1 Au/CeO4-C in the CO oxidation. And the apparent activation energies over the Au25/CeO2-C (60.5 kJ mol-1) is calculated to be about two-folds of these over the Au25/CeO2-R (28.6 kJ mol-1) and Au25/CeO2-P (31.3 kJ mol-1) catalysts. It is mainly tailored by the adsorbed [O] species on the ceria surface, namely, Au25/CeO2(002) and Au25/CeO2(111) were more active than Au25/CeO2(200) system in the CO oxidation. These insights at the molecular level may provide guidelines to the design of new oxide-supported nanogold catalysts for the aerobic oxidations.