Theoretical Investigation of the Functionalized MOene V₂O: A Density Functional Approach

The structural, thermodynamic, dynamical, and electronic properties of pristine and functionalized V₂O-based MOenes were investigated using density functional theory (DFT). Both 1T and 2H polymorphs were examined and functionalized with T = {Br, Cl, F, N, OH}. Our results reveal that the pristine 1T and 2H V₂O MOene phases are dynamically and thermodynamically stable. Among the high-symmetry adsorption sites, the HV site, where the functional group is positioned above the farthest vanadium atom, was identified as the most favorable for the 1T phase, while the H site, corresponding to a hollow position at the center of the hexagonal lattice, was found to be the most stable for the 2H phase. Phonon dispersion analyses confirmed that F- and OH- functionalized systems remain dynamically stable in both polymorphs, whereas Br-functionalization is stable only in the 2H phase. Based on cohesive and formation energies, the 2H configurations are thermodynamically more stable than the corresponding 1T phases. Interestingly, Br functionalization induces structural distortions and a metal-to-semiconductor transition, with an indirect band gap of 0.64 eV. Finally, lithium adsorption calculations show that the 2H phase presents favorable adsorption energies (E _ads ≈ -1.8 to -1.5 eV) with minimal lattice deformation, suggesting excellent reversibility for ion storage. The results establish V₂O-based MOenes as a new member of the emerging family of stable 2D oxides with tunable electronic properties and potential applications in energy storage and nanoelectronics.