Fabrication of surface-charged MXene membrane and its application for water desalination

Two-dimensional (2D) materials have been demonstrated as promising building blocks of designing high-performance membranes for molecular separation. Nevertheless, it is a big challenge to apply 2D-material membranes for water desalination. Herein, we proposed a new type of surface-charged MXene (SC-MXene) membrane for water desalination, which was facilely fabricated by laminar stacking of MXene nanosheets and subsequent surface-coating with polyelectrolyte layer. The morphology, physicochemical structure and surface property of the MXene materials and resulted membranes were observed by XPS, SEM, water contact angle test, AFM, IR and XPS. These results demonstrated that coating polyelectrolyte (PEI) successfully tuned the surface charge and enhanced the hydrophilicity without scarifying the laminar structure of MXene membrane. By utilizing the effects of electrostatic interaction and size-sieving, the resulting surface-charged MXene (SC-MXene) membrane exhibited high salt rejection and water permeance during either nanofiltration or forward osmosis process, showing great potential for water desalination.