Carrier Diffusion—The Main Contribution to Size-Dependent Photocatalytic Activity of Colloidal Gold Nanoparticles

Abstract

Harnessing hot carriers from photoexcited metallic nanoparticles for catalysis is very challenging because these carriers have extremely short lifetimes. Here, we demonstrate that smaller particles have higher surface-to-volume ratios that allow hot carriers to diffuse to particle surfaces with a higher probability and thereby exhibit higher photocatalytic activities as quantified by quantum yields. The measured photocatalytic activities for photoinduced etching of gold nanospheres by FeCl3, and the previously unreported aqueous hydrogenation of styrene using sodium borohydride under interband excitation show perfect dependence on the reciprocal of particle size. The size-dependent photocatalytic activity for photoinduced etching of gold nanospheres by FeCl3 under plasmon excitation, however, slightly deviates from this scaling law and may be influenced by other factors such as the surface field enhancement effect. This scaling law is expected to apply to other nanomaterial-based photocatalysts that rely on hot carrier diffusion to a surface for catalysis. Future design of nanomaterials for the harnessing of hot carriers for catalysis should take this scaling law into account.