Atomic-Scale Understanding Of The Na And Cl Remotion From Seawater Promoted By Mo1.33C(OH)2-Mxene

Abstract Drinking water scarcity in arid and semi-arid regions is a reality that may turn into a global healthcare problem in the next few years. The scientific community is always looking for new materials to achieve effective sea and brackish water desalination to reduce water scarcity. Commonly, theoretical and experimental methods make a synergy to better understand and explain the chemical and physical processes in water desalination electrodes. In this way, experimental evidence pointed to Mo1.33CTz MXene as an efficient ion intercalation material, in which both Na cations and Cl anions are removed. However, the atomic-scale understanding of the physico-chemical processes due to the cation and anion interaction with the MXene is still unknown. We report the Na cation and Cl anion interaction with an OH functionalized Mo1.33C monolayer through a comprehensive first-principles density functional theory assessment. Results demonstrate that Na atoms attach to Oxygen, whereas Cl atoms bond through hydrogen bonds to the functional groups in the Mxene, these bonds have two energy contributions: electrostatic and charge transfer, which increases its adsorption energy. Electrostatic potential isosurface calculations evidenced reactive sites. Oxygen atoms have an affinity for the electropositive Na atoms, whereas hydrogen atoms -of the hydroxyl groups- interact with the electronegative Cl atoms. Bader charge analysis and non-covalent interaction isosurfaces help clarifying the way cations and anions attach to the MXene layer. Our findings explain why OH-functionalized Mo1.33C can efficiently remove both anions and cations based on their affinities with the functional groups present in the MXene.