Atomic-Level Insights into the Edge Active ReS2 Ultrathin Nanosheets for High-Efficiency Light-to-Hydrogen Conversion

The development of highly active and reliable photocatalysts for solar hydrogen (H-2) production requires the thorough and in-depth understanding of the atomic-level structure/composition-performance relationship in photocatalysts. In this contribution, we for the first time develop a new and simple technique to prepare the ReS2 ultrathin nanosheets (UNSs) with massive atomic-level edge sites. The atomic-resolution scanning transmission electron microscopy integrated with density functional theory (DFT) based computations predicts that these atomic-level edge sites can efficiently boost H-2 evolution. Hence, the as-synthesized ReS2 UNSs are coupled with the three most extensively explored photocatalysts, i.e., TiO2, CdS, and melon, for apparently enhanced photocatalytic H-2 production. Particularly, the TiO2 decorated ReS2 UNS exhibits a significantly improved photocatalytic H-2-production rate of 1037 mu mol h(-1) g(-1), 129.6 times larger than that of bare TiO2. Moreover, the TiO2/ReS2 composites were investigated by both DFT-based calculations and state-of-art characterizations, e.g., synchrotron radiation based X-ray absorption near edge structure and transient-state surface photovoltage/photoluminescence spectroscopy. The results indicate that the abundant atomic-level edge active sites of ReS2 UNSs greatly advance the H-2 evolution while their relatively intact basal planes rapidly transfer the electrons to those edge active sites. Besides, the notable electronic coupling between ReS2 and TiO2 remarkably accelerates the dissociation/migration of photo-induced electron-hole pairs. Our work not only affords the atomic-level insights into the edge active sites of ReS2 UNSs in the photocatalysis field but also pave new avenues to the engineering of atomic-level reactive sites on two-dimensional materials for solar energy conversion.