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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