  Monolayer Mo$_2$C is a new member of two-dimensional materials. Here the
electronic structure and lattice dynamics of monolayer Mo$_2$C are calculated.
According to the electron-phonon interaction, it is predicted that monolayer
Mo$_2$C could be a quasi-two-dimensional superconductor and the effects of
functional-groups are crucially important considering its unsaturated surface.
Despite the suppressed superconductivity by chalcogen adsorption, our most
interesting prediction is that the electron-phonon interaction of monolayer
Mo$_2$C can be greatly enhanced by bromine absorbtion, suggesting that
Mo$_2$CBr$_2$ as a good candidate for nanoscale superconductor.
