Revealing the effects of terminal groups of MXene on the water desalination performance

The hydrophilicity as well as the charge nature can be tuned by manipulating the surface termination of MXene, which significantly affects the desalination of MXene membrane. However, the effects of termination group of MXene membrane on its water desalination performance are poorly understood. In this work, we adopted classic molecular dynamics (MD) simulation to systematically explore the influences of termination group, including fluorine (F), oxygen (O), and hydroxyl groups (OH), on the desalination performance of Ti₃C₂T_x membrane. The simulation results showed the surface charge features as well as the hydrogen bond interactions significantly influence the interactions between termination group and water. The water permeability through MXene channel with different surface terminations follows the order, F > O > OH. The charge nature of surface terminations also plays a vital role in their interactions with ions. The negative charge of surface terminations traps Na ⁺ ion both near the mouse and inside the channel of MXene membranes. As a result, MXene membranes possess distinctive Na⁺ ion rejection performance. After comparison, we conclude the desalination performance of Ti₃C₂F₂ is much better than traditional desalination membranes. Our work revealed the mechanisms responsible for the effects of termination type of MXene on water desalination performance, which might provide useful suggestions for the optimization of MXene membranes for water desalination.