Direct Synthesis of Large-Area 2D Mo2C on In Situ Grown Graphene

As a new member of the MXene group, 2D Mo₂C has attracted considerable interest due to its potential application as electrodes for energy storage and catalysis. The large-area synthesis of Mo₂C film is needed for such applications. Here, the one-step direct synthesis of 2D Mo₂C-on-graphene film by molten copper-catalyzed chemical vapor deposition (CVD) is reported. High-quality and uniform Mo₂C film in the centimeter range can be grown on graphene using a Mo–Cu alloy catalyst. Within the vertical heterostructure, graphene acts as a diffusion barrier to the phase-segregated Mo and allows nanometer-thin Mo₂C to be grown. Graphene-templated growth of Mo₂C produces well-faceted, large-sized single crystals with low defect density, as confirmed by scanning transmission electron microscopy (STEM) measurements. Due to its more efficient graphene-mediated charge-transfer kinetics, the as-grown Mo₂C-on-graphene heterostructure shows a much lower onset voltage for hydrogen evolution reactions as compared to Mo₂C-only electrodes.

The one-step direct synthesis of a 2D Mo₂C-on-graphene heterostructure by molten Cu-catalyzed chemical vapor deposition is reported. Graphene acts as a diffusion barrier to phase-segregated Mo, thus allowing the thickness of Mo₂C to be kinetically controlled. The heterostructure functions as a highly stable electrode in hydrogen evolution reactions.

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