Design of MoS₂/Graphene van der Waals Heterostructure as Highly Efficient and Stable Electrocatalyst for Hydrogen...

The thermodynamically stable phase of molybdenum disulfide (MoS₂) is evaluated as a promising and durable nonprecious-metal electrocatalyst toward the hydrogen evolution reaction (HER); however, its actual catalytic activity is restricted by an inert basal plane, low electronic conductivity, low density, and using efficiency of edged atoms. Moreover, 2D/2D van der Waals (vdws) heterostructures (HSs) with face-to-face contact can construct a highly coupled interface and are demonstrated to have immense potential for catalytic applications. In the present work, a 2D/2D hetero-layered architecture of an electrocatalyst, based on the alternate arrangement of ultrasmall monolayer MoS₂ nanosheets (approximately 5-10 nm) and ultrathin graphene (G) sheets, is prepared by a facilely chemical process, which is named as MoS₂/G HS. The unique structural characteristic of MoS₂/G HS is in favor of accommodating more active sites as the centers of ad/desorption hydrogen and transferring and separating the charges at a coupled interface to improve the electronic conductivity and durability. The density functional theory calculation results further confirm that the alternately arranged G layers and MoS₂ monolayers, as well as the expanded interplanar distance of 1.104 nm for MoS₂/G HS, can exhibit a superior HER performance in both 0.5 M H₂SO₄ and 1.0 M KOH.