Optimizing Ag-Pt core-shell nanostructures for solar energy conversion, plasmonic photocatalysis, and photothermal catalysis

Abstract

As a promising plasmonic photocatalyst, an Ag-Pt core-shell nanostructure is able to convert sunlight into chemical energy. To fully exploit each function of the constituent materials, a numerical study on the optimal design of the hybrid nanostructures is presented in this work. Ag-Pt is demonstrated to be a good material configuration for the core-shell nanostructure because Ag has strong intrinsic plasmonic responses and a low imaginary dielectric function in the visible region, while Pt is catalytically active and has a large imaginary dielectric function. Considering the hot carrier generation and transfer processes in both plasmonic photocatalysis and photothermal catalysis, the catalytically active sites at the Pt shell can be revealed by high local heating power densities. For the dipole resonance, these sites distribute alternately with the spots where local electric fields are greatly enhanced. The former are along the “equatorial belt” of the nanoparticle, while the latter are in the two polar regions. It is then found that the high-efficiency hot carrier generation is related to multiple factors, including at least an ultrathin shell and a core of high aspect ratio with sharp tips. The physics behind these factors is further addressed.