Manipulating Generation and Spatial Distribution of Plasmon-Generated Hot Electrons via Oxygen Vacancies on Au/TiO₂ Heterostructures for Photochemistry

Utilizing hot electrons on plasmonic metal/oxide heterostructures offers unique opportunities for solar photocatalysis. However, the role that surface oxygen vacancies (OVs) play in governing plasmon-driven photochemical reactions is poorly understood. Here, we demonstrate that surface OVs on Au/TiO₂ heterostructures manipulate plasmon-generated hot electrons in the generation process and spatial distribution for visible-light methylene blue (MB) degradation. Hot electrons originating from the plasmon-mediated electron transfer (PMET) pathway (i.e. the electron transfer from Au to TiO₂) and the plasmon-induced energy transfer (PIRET) pathway (i.e. the generation of electrons in TiO₂) accumulate under λ > 435 nm excitations, occupying surface OVs. Together, they result in ca. 5x enhancement in MB degradation than that under λ > 495 nm excitations, in which hot electrons only originate from the PMET pathway. Taken together, our study demonstrates an essential role played by surface OVs in plasmon-driven photochemistry and reveals two distinct mechanisms clarifying visible-light photocatalytic activity under different excitation conditions.