Identifying the Atomic Layer Stacking of Mo(2)C MXene by Probe Molecule Adsorption

[Image: see text] A density functional theory study is presented here aimed at investigating whether the atomic stacking on the new family of two-dimensional MXene materials has an influence on their adsorption properties and whether these properties can provide information about this structural feature. To this end, the Mo(2)C MXene, exhibiting two nearly degenerate crystal structures with either ABC or ABA atomic stacking, is chosen as a case study. The study of the adsorption of CO, CO(2), and H(2)O on both polymorphs of Mo(2)C reveals substantial differences that could be used in experiments to provide information about the atomic stacking of a given sample. Particularly, we show that the asymmetric and symmetric stretching modes of the adsorbed CO(2) and the CO stretching mode are clear features that allow one to identify the stacking of atomic layers of the Mo(2)C MXene. The present finding is likely to apply to other MXenes as well.