Surface extension of MeS₂ (Me=Mo or W) nanosheets by embedding MeS_x for hydrogen evolution reaction

Two-dimensional transition metal dichalcogenides (2D-TMDs), such as MoS₂ and WS₂ nanosheets (MeS₂-NS), are reported as efficient catalysts for hydrogen evolution reaction (HER), which can potentially replace the expensive platinum catalyst. In this report, 1T phase MeS₂ (1T-MeS₂) NS are synthesized by lithium-intercalation exfoliation method, subsequently being modified by amorphous MoS_x and WS_x (MeS_x@MeS₂-NS) through a solvothermal method. Interestingly, MeS_x@MeS₂-NS significantly improves the HER performance compared with bare MeS₂-NS as catalysts. Among these, MoS_x@MoS₂ is observed to be the best combination for HER, with an onset potential and Tafel slope of 114 mV and 45.1 mV decade⁻¹, respectively. The enhancement in the HER device using MeS_x@MeS₂-NS as the catalyst originates from vertically grown MeS_x, which provides additional active sulfur sites for the reaction, while inhibiting the restacking of MeS₂-NS. Furthermore, MoS_x@MoS₂-NS shows stable catalytic properties for HER after the 1000 cyclic test, without any observable changes. Thus, this study presents a facile method for the synthesis of 2D-TMD catalyst for HER towards large-scale and long-term stability for practical application.