The development of stable and low-cost catalysts with high reactivity to replace Pt-based ones is the central focus but challenging for hydrogen evolution reaction (HER). The incorporation of single atoms into two-dimensional (2D) supports has been demonstrated as an effective strategy because of the highly active single atomic sites and extremely large surface area of two-dimensional materials. However, the doping of single atoms is normally performed on the surface suffering from low stability, especially in acidic media. Moreover, it is experimentally challenging to produce monolayered 2D materials with atomic doping. Here, we propose a strategy to incorporate single foreign Fe atoms to substitute W atoms in sandwiched two-dimensional WS2. Because of the charge transfer between the doped Fe atom and its neighboring S atoms on the surface, the proximate S atoms become active for HER. Our theoretical prediction is later verified experimentally, showing an enhanced catalytic reactivity of Fe-doped WS2 in HER with the Volmer–Heyrovsky mechanism involved. We refer to this strategy as proximity catalysis, which is expected to be extendable to more sandwiched two-dimensional materials as substrates and transition metals as dopants.

Wafer-scale monolayer WS2 has been widely investigated. Here, we report a repeatable and low-cost one-step chemical vapor deposition method for the direct growth of a 4-in. monolayer WS2 film on a thermal oxide silicon wafer by using WO3 and H2S gas as precursors. H2S gas exhibits a high vulcanization ability and can effectively reduce the growth temperature of WS2 to 825 °C. The growth process follows a self-limiting growth to form a monolayer polycrystalline film, which is merged via many stable small-angle grain boundaries. The wafer-scale monolayer WS2 film shows uniform and high-quality electrical properties. This method helps promote the future production and application of wafer-scale monolayer sulfide.