Atomic-level insights into the edge active ReS₂ ultrathin nanosheets for high-efficiency light-to-hydrogen conversion

Abstract

The development of highly active and reliable photocatalysts for solar hydrogen (H2) 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 H2 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 H2 production. Particularly, the TiO2 decorated ReS2 UNS exhibits a significantly improved photocatalytic H2-production rate of 1037 μmol 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 H2 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.