Driving catalytic reactions with sunlight is an excellent example of sustainable chemistry. Gold nanocrystals have proven promising in harvesting solar energy for chemical reactions due to their extraordinary and tailorable localized surface plasmon resonance (LSPR) properties. Gold/semiconductor hybrid nanostructures have recently attracted much attention because of LSPR-induced light focusing in the vicinity of Au nanocrystals and/or plasmon induced charge transfer across the interface. CeO₂ has shown great potential in catalysis due to its attractive chemical and physical properties, including its unique 4f electron configuration and oxygen ion conductivity. Intimate integration of CeO₂ with Au nanocrystals at nanoscale is therefore expected to enable Au/CeO₂ to function as an excellent photocatalyst for desired catalytic reactions. However, the rational preparation of plasmonic Au/CeO₂ nanostructures has yet remained challenging. In addition, to fully improve the catalytic activity of Au/CeO₂ requires a thorough fundamental understanding of the underlying plasmon-enhanced mechanisms. We have recently performed systematic studies on the design of Au/CeO₂ with enhanced activities for the oxidation of alcohols and carried out investigations on the plasmon-enhanced mechanisms.

First, we developed a versatile approach for coating CeO₂ on monometallic Au and bimetallic Au@Pt, Au@Pd nanocrystals to produce multifunctional core@shell nanostructures with plasmon resonance wavelengths tunable from the visible to near-infrared region. The calcined (Au core)@(CeO₂ shell) nanostructures display high photocatalytic activities toward the oxidation of benzyl alcohol to benzaldehyde under the illumination of visible light. The enhanced photocatalytic activities are attributed to the synergistic effect between the Au nanocrystal core acting as a plasmonic component for efficient light harvesting and the CeO₂ shell providing catalytically active sites for the oxidation reaction.

Second, for core@shell structures, the effective accessibility of the active metal core by reactants is of particular importance. Dense shells might hinder hot holes in the Au core from being accessed by reactant molecules, which leads to the recombination of electrons and holes and therefore the reduction of photocatalytic activities. In this regard, mesoporous shell is of great promise since it offers a large number of continuous channels, high specific surface areas, and versatile pore structures. We successfully prepared mesoporous Au/CeO₂ microsphere photocatalysts with different Au loading amounts using an aerosol spray method. The mesoporous nature of CeO₂ endows the Au/CeO₂ sample with drastically boosted activities that are about 23 times larger than those of (Au nanosphere core)@(CeO₂ dense shell) nanostructures.

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[2] H. L. Jia, X. M. Zhu, R. B. Jiang, and J. F. Wang,* ACS Appl. Mater. Interfaces (2017), 9, 2560-2571.