(Invited) Multi-Electron Harvesting and Catalysis Using Plasmonic Nanoparticles: A Mechanistic Understanding

Abstract

Multi-electron redox reactions are known to be kinetically sluggish and there has been an ongoing search for synthetic catalysts for such reactions. In recent work from my laboratory, plasmonic nanoparticles have been found to photocatalyze multi-electron processes such as CO2 reduction and the condensation of ethylene to graphene. However, there is a need for mechanistic understanding and improved control of multi-electron-driven chemistry on plasmonic catalysts. We have studied in detail the transfer of hot electrons and holes from plasmonically excited nanoparticles to model redox species. We have found that under continuous light illumination and conditions favoring charge separation, plasmonic nanoparticles become significantly photocharged and multi-carrier harvesting becomes prevalent. Further, to understand the light-driven pathway for CO2 reduction on plasmonic nanoparticles, we have monitored the photoreaction in-situ on the single-nanoparticle-level using surface enhanced Raman scattering. From the reactive intermediate captured in the course of spectroscopic monitoring, the mechanism by which plasmonic excitation activates CO2 is beginning to be understood.