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.