Morphology effect of ceria supports on gold nanocluster catalyzed CO oxidation.

The interfacial perimeter is generally viewed as the catalytically active site for a number of chemical reactions over oxide-supported nanogold catalysts. Here, well-defined CeO 2 nanocubes, nanorods and nanopolyhedra are chosen to accommodate atomically precise clusters ( e.g. Au 25 (PET) 18 ) to give different Au cluster-CeO 2 interfaces. TEM images show that Au particles of ∼1.3 nm are uniformly anchored on the ceria surface after annealing in air at 120 °C, which can rule out the size hierarchy of nanogold in CO oxidation studies. The gold nanoclusters are only immobilized on the CeO 2 (200) facet in Au 25 /CeO 2 -C, while they are selectively loaded on CeO 2 (002) and (111) in the Au 25 /CeO 2 -R and Au 25 /CeO 2 -P catalysts. X-ray photoelectron spectroscopy (XPS) and in situ infrared CO adsorption experiments clearly demonstrate that the gold species in the Au 25 /CeO 2 samples are similar and partially charged (Au δ + , where 0 < δ < 1). It is observed that the catalytic activity decreases in the order of Au/CeO 2 -R ≈ Au/CeO 2 -P > Au/CeO 4 -C in the CO oxidation. And the apparent activation energy over Au 25 /CeO 2 -C (60.5 kJ mol -1 ) is calculated to be about two-fold of that over the Au 25 /CeO 2 -R (28.6 kJ mol -1 ) and Au 25 /CeO 2 -P (31.3 kJ mol -1 ) catalysts. It is mainly tailored by the adsorbed [O] species on the ceria surface, namely, Au 25 /CeO 2 (002) and Au 25 /CeO 2 (111) which were more active than the Au 25 /CeO 2 (200) system in the CO oxidation. These insights at the molecular level may provide guidelines for the design of new oxide-supported nanogold catalysts for aerobic oxidations.