Hydrazine Hydrate Intercalated 1T-Dominant MoS₂ with Superior Ambient Stability for Highly Efficient Electrocatalytic Applications

Metallic 1T-phase MoS₂ exhibits superior hydrogen evolution reaction (HER) performance than natural 2H-phase MoS₂ owing to its higher electrical conductivity and abundance of active sites. However, the reported 1T-MoS₂ catalysts usually suffer from extreme instability, which results in quick phase transformation at ambient conditions. Herein, we present a facile approach to engineer the phase of MoS₂ by introducing intercalated hydrazine. Interestingly, the as-synthesized 1T-dominant MoS₂ sample demonstrates excellent ambient stability without noticeable degradation for 3 months. Additionally, the 1T-dominant MoS₂ exhibits superior electrical conductivity (∼700 times higher than that of 2H-MoS₂) and improved electrochemical catalytic performance (current density ∼12 times larger than that of 2H-MoS₂ at an overpotential of 300 mV vs the reversible hydrogen electrode, RHE). Through experimental characterizations and density functional theory (DFT) calculation, we conclude that the stabilization of the metallic phase could be attributed to the electron donation from hydrazine molecules to the adjacent Mo atoms. The phase control strategy in this work provides a guideline to develop other highly efficient and stable two-dimensional (2D) electrocatalysts.