Trimetallic Nanostructures of Silver-Platinum Alloy Shells on Gold Nanorods for Plasmon-Mediated Photocatalysis

The localized surface plasmon resonances (LSPRs) in plasmonic nanoparticles have been used in accelerating photocatalytic reactions under light illumination. To improve the catalytic performance, bimetallic nanoparticles composed of a plasmonic core and a catalytic shell, where LSPR-excited hot electrons and the intrinsic catalytic active sites work synergistically, have attracted much attention. Despite progress in designing bimetallic catalysts, balancing the strong LSPR and catalytic sites remains challenging. Here, a trimetallic nanostructure containing a gold nanorod (AuNR) core and a silver-platinum (AgPt) hollow alloy shell was designed and used as a plasmon-mediated photocatalyst for methylene blue reduction reaction. Specifically, the AuNRs covered by a thin layer of Ag (Au@Ag) were used as the template to deposit Pt, forming a Au@AgPt trimetallic nanostructure. By changing the Ag and/or Pt precursor concentration, the external layer could be varied from AgPt heterostructure and AgPt hollow alloy shell to AuAgPt alloy dendrites. Using methylene blue as a model system, the photocatalytic reduction reaction was studied by adding the obtained nanoparticles as catalysts under visible and near-infrared light irradiation. The optimal photocatalytic performance of the trimetallic nanoparticles was seen with the AgPt hollow alloy shell, and the reaction rate is similar to 7 times higher than that of the reaction without catalysts and similar to 3 times higher than that of monometallic AuNRs, bimetallic Au@Ag, and Au@Pt nanorods. Plasmon energy transfer from the AuNRs to the AgPt layer, which enhances the charge-carrier generation, is responsible for outstanding photocatalytic performance. The approach used here to synthesize Au@AgPt trimetallic nanostructures is suitable for the design of other multimetallic photocatalysts.

Automated summary

A trimetallic nanostructure was designed and used as a plasmon-mediated photocatalyst. By optimizing the composition of the shell, nanoparticles with excellent catalytic performance were obtained.