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It was theoretically predicted that electric field intensities generated by surface plasmon resonance (SPR) around plasmonic metallic nanostructures could be reduced after covered by wide bandgap semiconductor, thus worsening the SPR-mediated photocatalytic activities. However, we found that the Ag nanocubes (Ag NCs) covered by AgCl demonstrated an abnormal SPR-mediated catalytic enhancement. Herein the PATP-to-DMAB oxidization was used as a model reaction to explore the photocatalytic conversions. It was observed that the Ag NCs covered by AgCl ultra-thin layer (AgCl@Ag NCs) presented better photocatalytic activities than those of individual Ag NCs under 633 nm excitation. To reveal the mechanism behind the superior activities of AgCl@Ag NCs, the PATP-to-DMAB conversions were also carried out in ambient argon (Ar), in which AgCl@Ag NCs demonstrated significantly higher conversions. These results could be interpreted based on the separation of electron-hole pairs in AgCl through SPR effect of Ag, where the electrons in the valence band of AgCl were excited to the empty states of Ag, leaving holes in the semiconductor and resulting in the oxidation of PATP to DMAB. Thus our findings may provide a novel way to enhance SPR-mediated photocatalytic activities on plasmonic metallic nanostructures by the cover of an ultra-thin layer of wide bandgap semiconductor.

The localized surface plasmon resonance (LSPR) excitation in plasmonic nanoparticles has been used to accelerate several catalytic transformations under visible-light irradiation. In order to fully harness the potential of plasmonic catalysis, multimetallic nanoparticles containing a plasmonic and a catalytic component, where LSPR-excited energetic charge carriers and the intrinsic catalytic active sites work synergistically, have raised increased attention. Despite several exciting studies observing rate enhancements, controlling reaction selectivity remains very challenging. Here, by employing multimetallic nanoparticles combining Au, Ag, and Pt in an Au@Ag@Pt core–shell and an Au@AgPt nanorattle architectures, we demonstrate that reaction selectivity of a sequential reaction can be controlled under visible light illumination. The control of the reaction selectivity in plasmonic catalysis was demonstrated for the hydrogenation of phenylacetylene as a model transformation. We have found that the localized interaction between the triple bond in phenylacetylene and the Pt nanoparticle surface enables selective hydrogenation of the triple bond (relative to the double bond in styrene) under visible light illumination. Atomistic calculations show that the enhanced selectivity toward the partial hydrogenation product is driven by distinct adsorption configurations and charge delocalization of the reactant and the reaction intermediate at the catalyst surface. We believe these results will contribute to the use of plasmonic catalysis to drive and control a wealth of selective molecular transformations under ecofriendly conditions and visible light illumination.