Spatially confined synthesis of large-sized MoS₂ nanosheets in molten KSCN toward efficient hydrogen evolution

Abstract Low-temperature KSCN molten salt is a promising technique to synthesize defect-rich MoS₂ catalysts for hydrogen evolution reaction (HER). However, owing to the fast ion diffusion rate for rapid crystal growth, the resultant catalysts show a morphology of microsphere, which aggregates from MoS₂ nanosheets, to suppress the catalytic performance. In this work, large-sized few-layer MoS₂ nanosheets are synthesized via a spatial confinement strategy by adding inert NaCl into the KSCN molten salt. With the NaCl spacer to physically block the long-distance ion diffusion and isolate the chemical reaction, the MoS₂ nucleation and subsequent crystal growth could be controlled, guiding the nanosheets to grow along the narrow gap between the NaCl crystals to avoid aggregation. As a result, ultrathin MoS₂ nanosheets with a large geometry size are constructed. Profiting from the architecture to expose active sites and boost charge transfer kinetics, the large-sized few-layer MoS₂ nanosheets exhibit an impressive HER performance, showing a small η ₁₀ of 160 mV and a low Tafel slope of 53 mV dec⁻¹ with excellent stability. This work provides not only an efficient HER catalyst but also a facile spatial confinement technique to design and synthesize a large spectrum of transition metal sulfides for broad uses.