In Situ Thermal Synthesis of Inlaid Ultrathin MoS₂/Graphene Nanosheets as Electrocatalysts for the Hydrogen Evolution Reaction

Herein, we report a unique thermal synthesis method to prepare a novel two-dimensional (2D) hybrid nanostructure consisting of ultrathin and tiny-sized molybdenum disulfide nanoplatelets homogeneously inlaid in graphene sheets (MoS₂/G) with excellent electrocatalytic performance for HER. In this process, molybdenum oleate served as the source of both molybdenum and carbon, while crystalline sodium sulfate (Na₂SO₄) served as both reaction template and sulfur source. The remarkable integration of MoS₂ and graphene in a well-assembled 2D hybrid architecture provided large electrochemically active surface area and a huge number of active sites and also exhibited extraordinary collective properties for electron transport and H⁺ trapping. The MoS₂/G inlaid nanosheets deliver ultrahigh catalytic activity toward HER among the existing electrocatalysts with similar compositions, presenting a low onset overpotential approaching 30 mV, a current density of 10 mA/cm² at ∼ 110 mV, and a Tafel slope as small as 67.4 mV/dec. Moreover, the strong bonding between MoS₂ nanoplatelets and graphene enabled outstanding long-term electrochemical stability and structural integrity, exhibiting almost 100% activity retention after 1000 cycles and ∼ 97% after 100 000 s of continuous testing (under static overpotential of -0.15 V). The synthetic strategy is simple, inexpensive, and scalable for large-scale production and also can be extended to diverse inlaid 2D nanoarchitectures with great potential for many other applications.