Hydrazine hydrate-assisted adjustment of sulfur-rich MoS2 as hydrogen evolution electrocatalyst

The activity of MoS2 toward hydrogen evolution reaction (HER) originated from different sulfur configurations and phases. Metallic 1T phase of MoS2 with good electronic conductivity and abundant electrocatalytic active sites is favorable for electrocatalysis. In addition, bridging S22- has been verified as the major active sites for HER. However, there is a lack of in-depth understanding for the coexistence of 1T phase and bridging S22- of MoS2. Herein, a facile hydrazine hydrate-assisted method is reported to synthesize sulfur-rich MoS2. Specifically, when higher ratio of 1T to 2H phase was obtained, a higher proportion of bridging S22- to terminal S22- was produced simultaneously. With an optimum amount of hydrazine hydrate, MoS2 exhibits a low overpotential of 173 mV at a current density of 10 mA cm−2, a small Tafel slope of 56.6 mV dec−1, and long-term stability in 0.5 M H2SO4 solution. This work provides a new insight for improving the electrocatalytic activity of MoS2 via a simple method.