MoS 2 Quantum Dot Growth Induced by S Vacancies in a ZnIn 2 S 4 Monolayer: Atomic-Level Heterostructure for Photocatalytic Hydrogen Production.

It is highly demanded to steer the charge flow in photocatalysts for efficient photocatalytic hydrogen reactions (PHRs). In this study, we developed a smart strategy to position MoS2 quantum dots (QDs) at the S vacancies on a Zn facet in monolayered ZnIn2 S4 (Vs-M-ZnIn2 S4 ) to craft a two-dimensional (2D) atomic-level heterostructure (MoS2 QDs@Vs-M-ZnIn2 S4 ). The electronic structure calculations indicated that the positive charge density of the Zn atom around the sulfur vacancy (Vs) was more intensive than other Zn atoms. The Vs confined in monolayered ZnIn2 S4 established an important link between the electronic manipulation and activities of ZnIn2 S4 . The Vs acted as electron traps, prevented vertical transmission of electrons, and enriched electrons onto the Zn facet. The Vs-induced atomic-level heterostructure sewed up vacancy structures of Vs-M-ZnIn2 S4 , resulting in a highly efficient interface with low edge contact resistance. Photogenerated electrons could quickly migrate to MoS2 QDs through the intimate Zn-S bond interfaces. As a result, MoS2 QDs@Vs-M-ZnIn2 S4 showed a high PHR activity of 6.884 mmol g-1 h-1 , which was 11 times higher than 0.623 mmol g-1 h-1 for bulk ZnIn2 S4 , and the apparent quantum efficiency reached as high as 63.87% (420 nm). This work provides a prototype material for looking into the role of vacancies between electronic structures and activities in 2D photocatalytic materials and gives insights into PHR systems at the atomic level.