Atomically precise Ag25(SR)18 nanoclusters: a stable photosensitizer for photocatalysis†

Abstract

Atomically precise metal nanoclusters (NCs) for use as photosensitizers in photocatalysis have attracted considerable attention due to their quantum confinement effect, unique atom-stacking fashion, and enriched catalytic active sites, which make them promising photosensitizers for solar energy conversion. However, current works on metal NC-based photocatalytic systems are still in their infancy owing to the complex synthetic strategies of metal NCs and deficiency of metal NCs with a favorable energy level configuration, which substantially limit the exploration of metal NC photocatalytic systems, while the photocatalytic mechanism remains elusive. Herein, we conceptually demonstrate the construction of a metal NC/transition metal chalcogenide (TMC) binary heterostructure photosystem via electrostatic self-assembly under ambient conditions, wherein Ag₂₅(SR)₁₈ NCs (SR: 2,4-dimethylbenzenethiol) were precisely and uniformly anchored on the surface of TMCs to function as light-harvesting antenna. We ascertained that advantageous charge transfer between the TMCs and Ag₂₅(SR)₁₈ NCs resulted in a prolonged charge lifetime and increased carrier density. Therefore, self-assembled metal NCs/TMCs heterostructures demonstrated significantly improved and versatile photoactivities toward the anaerobic photoreduction of aromatic nitro compounds to amino derivatives and heavy metal ion (Cr⁶⁺) reduction under visible light. Our work clarifies the photocatalytic mechanism of atomically precise metal NC photocatalysis and opens up new avenues for smartly mediating the charge transfer and separation of metal NCs for solar energy conversion.