Underlying Mechanisms of Hot Carrier-Driven Reactivity on Bimetallic Nanostructures

Abstract

Bimetallic nanostructures exhibit unique catalytic activity and selectivity that are not evident for their monometallic analogues. Such nanostructures contain plasmonic metals, such as gold or silver, which afford highly efficient harvesting of electromagnetic radiation and its conversion into hot carriers. These highly energetic species are transferred to the catalytic metal subcomponent of the bimetallic nanostructure, where a large spectrum of chemical reactions may be catalyzed. The strength of the electric field and the interplay between catalytic and plasmonic metals at the nanoscale are thus critically important for the catalytic activity of bimetallic nanostructures. In this study, we investigate the relationship between the catalytic activity and local electric fields sustained on the surface of gold–palladium (Au@PdNPs) and gold–platinum (Au@PtNPs) nanoplates using tip-enhanced Raman spectroscopy. We image the spatially varying magnitudes of rectified (DC) local electric fields on the surface of these nanostructures and compare them to the fields sustained on the surface of monometallic nanoplates. We find substantially larger electric field magnitudes on Au@PdNPs and Au@PtNPs as compared to their monometallic analogues. These findings suggest that catalytic efficiency of bimetallic nanostructures may be mediated and potentially tuned through precise control of electric fields sustained on their surfaces.