Hot Holes Assist Plasmonic Nanoelectrode Dissolution

Abstract

Strong light absorbing properties, and the ability to drive electrochemical reactions on their surface has sparked, allow plasmonic metal nanoparticles to serve as photocatalysts. After plasmon excitation, hot charge carriers are generated in the metal nanoelectrode, driving electrochemical reactions. To achieve plasmonic photocatalysis, the hot charge carriers must be harnessed before they decay by giving off heat to the surroundings. Here, we demonstrate the role of photogenerated hot holes in oxidative electrodissolution of individual gold nanorods in chloride electrolyte. We monitor the plasmon resonance spectroscopically using snapshot hyperspectral imaging with millisecond time resolution, while electrochemically tuning charge carrier density. We show that light induced hot charge carriers enhance the rate of gold oxidation and subsequent electrodissolution tenfold. Importantly, we find that hot holes generated from interband transitions compared to holes in the sp-band around the Fermi level contribute to electro-oxidation. We further show that the reaction onset potential cannot be lowered below the chloride onset potential, demonstrating that electrochemical mediation is required. These results provide new insights into hot hole driven photocatalysis while emphasizing the need for statistical descriptions of electrochemical non-equilibrium processes on innately heterogeneous nanoparticle supports. Figure: Schematic representation of experimental setup and mechanism. a: when positive potentials are applied while illuminating the nanoparticle, the scattering intensity and hence volume of the nanoparticle decreases (see inset). b: photo-generated hot holes inject into the HOMO of adsorbed chloride. Figure 1