Spatially confined synthesis of large-sized MoS 2 nanosheets in molten KSCN toward efficient hydrogen evolution.

Low-temperature KSCN molten salt is a promising technique to synthesize defect-rich MoS 2 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 MoS 2 nanosheets, to suppress the catalytic performance. In this work, large-sized few-layer MoS 2 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 MoS 2 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 MoS 2 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 MoS 2 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.