Fine‐tuning strain and vacancies in 2H‐phase transition‐metal dichalcogenides, although extremely challenging, is crucial for activating the inert basal plane for boosting the hydrogen evolution reaction (HER). Here, atomically curved 2H‐WS2 nanosheets with precisely tunable strain and sulfur vacancies (S‐vacancies) along with rich edge sites are synthesized via a one‐step approach by harnessing geometric constraints. The approach is based on the confined epitaxy growth of WS2 in ordered mesoporous graphene derived from nanocrystal superlattices. The spherical curvature imposed by the graphitic mesopores enables the generation of uniform strain and S‐vacancies in the as‐grown WS2 nanosheets, and simultaneous manipulation of these two key parameters can be realized by simply adjusting the pore size. In addition, the formation of unique mesoporous WS2@graphene van der Waals heterostructures ensures the ready access of active sites. Fine‐tuning the WS2 layer number, strain, and S‐vacancies enables arguably the best‐performing HER 2H‐WS2 electrocatalysts ever reported. Density functional theory calculations indicate that compared with strain, S‐vacancies play a more critical role in enhancing the HER activity.
Discretely sized semiconductor clusters have attracted considerable attention due to their intriguing optical properties and self-assembly behaviors. While lead halide perovskite nanostructures have been recently intensively explored, few studies have addressed perovskite clusters and their self-assembled superstructures. Here, we report the room-temperature synthesis of sub-2 nm CsPbBr clusters and present strong evidence that these ultrasmall perovskite species, obtained under a wide range of reaction conditions, possess a specific size, with optical properties and self-assembly characteristics resembling those of well-known II-VI semiconductor magic-sized clusters. Unlike conventional CsPbBr nanocrystals, the as-synthesized CsPbBr nanoclusters spontaneously self-assemble into a hexagonally packed columnar mesophase in solution, which can be further converted to single-crystalline CsPbBr quantum nanoribbons with bright deep-blue emission at room temperature. Such a conversion of CsPbBr nanoclusters to nanoribbons is found to be driven by a ligand-destabilization-induced crystallization and mesophase transition process. Our study will facilitate the investigation of perovskite nanoclusters and offer new possibilities in the low-temperature synthesis of anisotropic perovskite nanostructures.
Transition metal dichalcogenides (TMDs) are promising anode materials for sodium-ion batteries (SIBs), but suffer from low rate capability and poor cycling stability. Here, we describe our efforts in designing a...
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