Elucidating the Origin of Plasmon-Generated Hot Holes in Water Oxidation

Plasmon-generated hot electrons in metal/oxide heterostructures have been used extensively for driving photochemistry. However, little is known about the origin of plasmon-generated hot holes in promoting photochemical reactions. Herein, we discover that, during the nonradiative plasmon decay, the interband excitation rather than the intraband excitation generates energetic hot holes that enable to drive the water oxidation at the Au/TiO2 interface. Distinct from lukewarm holes via the intraband excitation that only remain on Au, hot holes from the interband excitation are found to be transferred from Au into TiO2 and stabilized by surface oxygen atoms on TiO2, making them available to oxidize adsorbed water molecules. Taken together, our studies provide spectroscopic evidence to clarify the photophysical process for exciting plasmon-generated hot holes, unravel their atomic-level accumulation sites to maintain the strong oxidizing power in metal/oxide heterostructures, and affirm their crucial functions in governing photocatalytic oxidation reactions.

Automated summary

Plasmon-generated hot holes in metal/oxide heterostructures, which play a crucial role in promoting photochemical reactions, are found to be generated from the interband excitation during the nonradiative plasmon decay. These hot holes can penetrate into TiO2 and be stabilized by surface oxygen atoms, enabling them to oxidize water molecules. This study provides spectroscopic evidence for the photophysical process of plasmon-generated hot holes and elucidates their accumulation sites and functions in photocatalytic oxidation reactions.