Research progress of 1T-MoS2 in electrocatalytic hydrogen evolution

Hydrogen production from electrochemical water electrolysis is one of the most effective solutions to the world's energy dilemma and environmental degradation. Transition metal dichalcogenides (TMDs) have been extensively reported as effective catalysts for hydrogen production, Molybdenum disulfide (MoS2) has particularly evoked widespread interest due to its high activity, low cost, and plentiful components. For MoS2, it commonly has the semiconductor phase (2H) and the metallic phase (1T) structures, and 2H is more stable but less conductive than 1T. Although more favorable for electronic transfer, 1T-MoS2 has poor stability, complex preparation, a restricted number of active sites, low intrinsic catalytic activity, and poor interlayer conductivity. In this review, we will discuss the phase transition mechanism from 2H–MoS2 to 1T-MoS2, along with recent research advances. Because it is a technical challenge to synthesize the1T-MoS2, we will discuss the characteristics and structure of 1T-MoS2 in detail and its application in water electrolysis cataloging on the preparation methods. The improved intrinsic activity, increased active sites, and the improvement of conductivity are discussed in terms of several aspects including (1) doping and ionic intercalation, (2) introduction of S vacancies (Vs) and defect modification, (3) highly conductive substrates and composite structures combination, as well as (4) phase transition effect. The critical difficulties and prospects are also presented at the end of this review, providing further solutions and inspirations for the preparation of 1T-MoS2 electrocatalysts with enhanced catalytic performance.