Insight into the Unique Role of Silver Single-Atom in Atomic-Thickness ZnIn2S4/g-C3N4 Van Der Waals Heterojunction for Photocatalytic Hydrogen Evolution

The construction of ultra-close 2D atomic-thickness Van der Waals heterojunctions with high-speed charge transfer still faces challenges. Here, we synthesized single-layer ZnIn2S4 and g-C3N4, and introduced silver single atoms to regulate Van der Waals heterojunctions at the atomic level to optimize charge transfer and catalytic activity. At the atomic scale, the impact of detailed structural differences between the two characteristic surfaces of ZnIn2S4 ([Zn-S4] and [In-S4]) on catalytic performance has been first proposed. Experiments combined with the DFT study demonstrate that single atom Ag not only acts as a charge transfer bridge but also regulates the energy band and intrinsic catalytic activity. Benefiting from the enhanced electron delocalization, the synthesized catalyst ZIS/Ag@CN exhibits excellent photocatalytic performance, with a hydrogen production rate of 5.50 mmol·g−1·h−1, which is much higher than the reported Ag-based single-atom catalysts so far. This work provides a new understanding of atomic-level heterojunction interface regulation and modification.