Space-Confined Growth of MoS₂ Nanosheets within Graphite: The Layered Hybrid of MoS₂ and Graphene as an Active Catalyst for Hydrogen Evolution Reaction

Abstract

Since the electrocatalytic activity of layered molybdenum disulfide (MoS₂) for hydrogen evolution reaction (HER) closely depends on its exposed edges, the morphology and size of the material are critically important. Herein, we introduce a novel solvent-evaporation-assisted intercalation method to fabricate the hybrid of alternating MoS₂ sheets and reduced graphene oxide layers, in which the nanosize of the MoS₂ nanosheets can be effectively controlled by leveraging the confinement effect within the two-dimensional graphene layers. Significantly, the resulting MoS₂/reduced graphene oxide (RGO) composite shows excellent catalytic activity for HER characterized by higher current densities and lower onset potentials than the conventional pre-exfoliated RGO supported MoS₂ nanosheets. Further experiments on the effect of oxidation degree of graphene, the crystallinity of MoS₂, and the exposed active site density on the HER performance of the MoS₂/RGO composites show that there is an optimum condition for the catalytic activity of HER due to a balance between the numbers of exposed active sites of MoS₂ and the internal conductive channels provided by graphene