Molecular simulation of water permeation and salt rejection for MoS2 nanoslit membranes

Abstract

Molybdenum disulfide (MoS2) layer-stacked membranes have gained considerable attention due to their chemical stability and water permeability in desalination processes. However, molecular transport across slit gaps between edge-to-edge MoS2 nanosheets remains unexplored. It is suspected that edge chemistry in MoS2 slits could be important in the MoS2 desalination membranes. Herein, molecular simulations were performed to investigate water permeation and salt rejection for the MoS2 slits with different edge patterns and slit spacings. It is demonstrated that MoS2 nanoslits could realize high water permeation and efficient ion rejection, in particular, the SS edge slit shows excellent desalination efficiency. The water permeation across MoS2 slits could be attributed to the confined water structures and the surface slips on the edge patterns, both of which are influenced by different surface interactions. The free energy landscapes were simulated to characterize the thermodynamics resistance for ions passing through MoS2 nanoslits. The salt rejection is the combining contributions from the ion hydration interaction and the MoS2 slit interaction, wherein the Coulombic interaction provides the critical influence. Overall, our work will hopefully pave the way for design in applications of MoS2 desalination membranes.