Defect-rich 1T-MoS2 nanosheets towards efficient electrochemical hydrogen evolution by simultaneous phase and defect engineering

Molybdenum sulfide (MoS2) has been considered as a promising candidate to replace Pt for the electrochemical hydrogen evolution reaction (HER). However, the disadvantages of inert basal planes and low conductivity limit its application in HER. Herein, we report a facile strategy to achieve simultaneous phase transition and defect engineering in MoS2 by adjusting the ratio of sulfur precursor to molybdenum precursor in the synthesis process. The excess thiourea are adsorbed on the surface of as-formed MoS2 nanocrystallites, which hinders the further crystallization process and creates a large amount of defects on the basal planes. Besides, ammonia ions could in situ insert into the interlayers of MoS2 and induce a phase transition from 2H-MoS2 to 1T-MoS2. The optimized defect-rich 1T-MoS2 catalyst shows a small overpotential of 232 mV at 10 mA cm(-2) and Tafel slope of 61 mV dec(-1) in acidic media. The superior HER activity is attributed to the defect-rich and 1T-phase structure, which contributes significantly enhanced electronic conductivity and greatly exposed active sites.