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 ReS 2 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 ReS 2 UNSs are coupled with the three most extensively explored photocatalysts, i.e., TiO 2, CdS, and melon, for apparently enhanced photocatalytic H 2 production. Particularly, the TiO 2 decorated ReS 2 UNS exhibits a significantly improved photocatalytic H 2 -production rate of 1037 μmol h –1 g –1, 129.6 times larger than that of bare TiO 2 . Moreover, the TiO 2 /ReS 2 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 ReS 2 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 ReS 2 and TiO 2 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 ReS 2 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.