  MXene-based heterostructures have received considerable interest owing to
their unique properties. Herein, we examine various heterostructures of a
prototypical MXene and graphene using density functional theory. We find that
the adhesion energy, charge transfer, and band structure of these
heterostructures are sensitive not only to the surface functional group, but
also to the stacking order. Difference in work function dictates the direction
and amount of electron transfer across the interface, which causes a shift in
the Dirac point of the graphene bands in the heterostructures of monolayer
graphene and monolayer MXene. In the heterostructures of bilayer graphene and
monolayer MXene, the interface breaks the symmetry of the bilayer graphene; in
the case of the AB-stacking bilayer, the electron transfer leads to an
interfacial electric field that opens up a gap in the graphene bands at the K
point. This internal polarization strengthens both the interfacial adhesions
and the cohesion between the two graphene layers. The MXene-graphene-MXene and
graphene-MXene-graphene sandwich structures behave as two mirror-symmetric
MXene-graphene interfaces. Our first principles studies provide a comprehensive
understanding for the interaction between a typical MXene and graphene.
