Effect of intercalated graphene sheet on the desalination performance of a graphene channel

Graphene-based materials, with their exceptional physicochemical properties, have demonstrated great potential in desalination. However, conventional graphene membranes face a trade-off between water permeability (WP) and salt rejection, which imposes certain limitations on their overall water treatment performance. In this study, we employ molecular dynamics simulations to demonstrate a strategically engineered intercalated-graphene channel that synergistically combines ultra-high water transport capacity with exceptional ion rejection (IR) capabilities. An interesting phenomenon we observed is that as the intercalation position changes, the salt rejection of the device exhibits a pronounced peak behavior. For small-sized channels, this can be primarily attributed to the high energy barrier for ion transport caused by the dehydration-reassociation process, which effectively blocks ions. For large-sized channels, where the dehydration process is weak, the primary barrier to ion diffusion arises from changes in the water layer structures, because water and ions are coupled, moving together as a co-transport system. Additionally, both water and ion flux exhibit a linear increase with pressure difference (ΔP), aligning with the predictions of the ideal Hagen-Poiseuille equation. Overall, in the best-performing system, the IR remains above 93.1% even as the ΔPincreases, while maintaining high WP, effectively achieving a balance between both factors. Our findings highlight how sub-nanometer geometric structure control can fundamentally alter transport physics in desalination meters.