Understanding the Behaviors of Plasmon-Induced Hot Carriers and Their Applications in Photocatalysis.

Photocatalysis driven by plasmon-induced hot carriers has been gaining increasing attention. Recent studies have demonstrated that plasmon-induced hot carriers can directly participate in photocatalytic reactions, leading to great enhancement in solar energy conversion efficiency, by improving the catalytic activity or changing selectivity. Nevertheless, the utilization efficiency of hot carriers remains unsatisfactory. Therefore, how to correctly understand the generation and transfer process of hot carriers, as well as accurately differentiate between the possible mechanisms, have become a key point of attention. In this review, we overview the fundamental processes and mechanisms underlying hot carrier generation and transport, followed by highlighting the importance of hot carrier monitoring methods and related photocatalytic reactions. Furthermore, possible strategies for the further characterization of plasmon-induced hot carriers and boosting their utilization efficiency have been proposed. We hope that a comprehensive understanding of the fundamental behaviors of hot carriers can aid in designing more efficient photocatalysts for plasmon-induced photocatalytic reactions.

Direct S-H Evidence Revealing the Photo-electrocatalytic Hydrogen Evolution Reaction Mechanism on CdS Using Surface-Enhanced Raman Spectroscopy.

Photoelectrocatalytic water splitting using metal sulfides is a promising method for green hydrogen production. However, in situ probing of the hydrogen evolution reaction (HER) on sulfides with excellent performance remains a challenge. Here, we construct Au@CdS core-shell nanoparticles to study the HER on CdS, a typical HER catalyst, by surface-enhanced Raman spectroscopy (SERS) using a "borrowing" strategy. We directly capture the spectroscopic evidence of S-H intermediate under HER condition, further verified by isotopic experiments. Moreover, the population of S-H intermediates is improved by injecting charge carriers through light illumination and the S-H bond is weakened by introducing Pt to form a Au@Pt@CdS structure to change the interfacial electronic structure, both of them resulting in significant HER performance improvement. These findings can deepen the understanding of the HER mechanism and offer strategies for designing of cost-effective HER catalyst with high performance.

In Situ Raman Probing of Hot-Electron Transfer at Gold-Graphene Interfaces with Atomic Layer Accuracy.

Plasmonic metals under photoexcitation can generate energetic hot electrons to directly induce chemical reactions. However, the capability and fundamental insights of the transportation of these hot electrons at plasmonic metal-2D material interfaces remain unclear. Herein, hot-electron transfer at Au-graphene interfaces has been in situ studied using surface-enhanced Raman spectroscopy (SERS) with atomic layer accuracy. Combining in situ SERS studies with density functional theory calculations, it is proved that hot electrons can be injected from plasmonic Au nanoparticles to graphene and directly penetrate graphene to trigger photocatalytic reactions. With increasing graphene layers, the transportation of hot electrons decays rapidly and would be completely blocked after five layers of graphene. Moreover, the transfer of hot electrons can be modulated by applying an external electric field, and the hot-electron transfer efficiency under electrochemical conditions is improved by over three times in the presence of a monolayer of graphene.