Why is Single-Layer MoS₂ a More Energy Efficient Membrane for Water Desalination?

Water desalination technologies are extensively utilized to solve water scarcity problems in many regions of the world. Discovery and application of two-dimensional (2D) nanoporous materials provide engineers a viable solution for reducing to a large extent energy consumption during the water desalination process. In this work, we conducted a thorough comparison of the water permeability and ion rejection rate between various 2D materials, including MoS₂, graphene, phosphorene, boron nitride, and MoSe₂. Through molecular dynamics simulation, we demonstrated that among all 2D materials with the same pore size, single-layer MoS₂ consistently performs 27% better than graphene, 38% than phosphorene, 35% than BN, and 20% than MoSe₂ in terms of water permeability while maintaining a greater than 99% ion rejection rate. We further investigated how the fundamental physics behind the outstanding performance of MoS₂ is a combination of water structure and dynamics near the membrane surface, energy barrier, and water packing and velocity inside the nanopore.