Superatomic Layer of Cubic MoS Clusters Connected by Cl Cross-Linking.

Superatomic clusters - assemblies of atoms with various sizes, shapes, and compositions - can form hierarchical architectures that exhibit emergent electronic properties not found in their individual units. In particular, cubic MX clusters of chalcogenides (M = transition metal; X = chalcogen) are recognized as versatile building blocks for 3D structures with tunable morphologies and electronic properties. However, tetrahedral MX clusters rarely assemble into 2D architectures, which could offer a distinct class of functional materials from their 3D analogues. Here, this work reports the preparation of 2D MoSCl, a superatomic layer with a sandwich structure consisting of MoS clusters interconnected through Cl cross-linking. The vapor-phase reaction inside nanotubes promotes the selective growth of MoSCl nanoribbons, allowing detailed characterization via transmission electron microscopy. This methodology can be applied to the growth of layered structures containing MoSCl at the micrometer scale. This work has demonstrated that mono- and few-layer MoSCl can be prepared by exfoliation of parent solids. Electronic structure calculations indicate that the 2D monolayer has quasi-flat bands, giving rise to an indirect-to-direct bandgap transition under mechanical strain. Furthermore, scanning electrochemical microscopy reveals the potential of the layered structures as highly efficient catalysts for the hydrogen-evolution reaction.