Ethylenediamine-assisted phase engineering of 1T/2H–MoS2/graphene for efficient and stable electrocatalytic hydrogen evolution

Abstract

1T-MoS2 exhibits superior eletroconductivity and electrocatalytic activity in hydrogen evolution reaction (HER) over 2H–MoS2. But its thermodynamic instability severely hinders its practical application. This paper develops a highly active and stable triphasic 1T/2H–MoS2/graphene heterostructure through a facile one-step hydrothermal route with the assistance of a small organic molecule, ethylenediamine, as the structure-directing reagent. The novel triphasic heterostructure is fabricated by vertically stacking lateral 1T/2H–MoS2 heterojuctions on graphene. The stability of the 1T phase is associated with the strain effects in the lateral 1T/2H–MoS2 heterojunctioned nanosheets and the electron coupling effects in the vertical 1T/2H–MoS2/graphene 2D/2D heterostructure. The content of 1T phase in 1T/2H–MoS2/graphene can be regulated by adjusting the preparation temperature. The optimized 1T/2H–MoS2/graphene hybrid contains 40.5% 1T phase and exhibits outstanding HER performance with a low overpotential of 143 mV at current density of 10 mA cm-2, a small Tafel slope of 64 mV dec-1 and excellent durability in acid electrolyte. This work highlights a new strategy to utilize structure-directing reagents for fabricating highly efficient MoS2-based electrocatalysts.