Wafer-Scale Manufacturing of Ultrathin Nanoporous Transition Metal Dichalcogenide Membranes Using Chemical Etching for Water Purification and Other Applications

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This advanced manufacturing grant supports research in novel ultrathin membranes for efficient water purification. This work focuses on large-area manufacturing of ultra-thin transition metal dichalcogenide membranes to improve the precision of water filtration and treatment. This project creates new fundamental knowledge through the understanding of the mechanisms of water molecule and ion motion at atomic scales in these improved membranes. An important motivation for decreasing the membrane thickness is that it leads to increased water fluxes. The membranes are made by chemical vapor deposition of transition metal dichalcogenides on foils, followed by chemical etching in acids to make them nanoporous. Besides water purification, this work is anticipated to impact other applications where membranes are used such as gas and biomolecule filtration. This project leverages research outcomes for education and outreach. Outreach to the broad nanomaterials community and to membrane industry involves sharing of manufacturing processing data. The educational component provides innovative multidisciplinary learning opportunities for students at all levels at the crossroads of solid-state physics, materials science and high-resolution microscopy. Student outreach includes presentations to high school students and participation in STEM activities.This grant supports advanced manufacturing of two-dimensional (2D) nanomaterials towards creating novel cm-scale membranes, in which monolayers are supported by robust few-layer membranes. Two-dimensional nanomaterials, such as, transition metal dichalcogenides, have demonstrated potential for many applications from defect-free materials for electronics to defect-engineered materials for membrane separation technologies like water desalination and gas separation. Current fabrication of 2D nanoporous membranes is often limited in terms of control or rely on the use of ion and electron beam irradiation, which is slow and costly. This work uses simple chemical etching to make holes in membranes using an industrial wet etchant, leading to controllable membrane porosity and economic manufacturing. This research answers key scientific questions about fundamental properties of ion flow as a function of membrane properties, thickness, pore size and density towards efficient water desalination in comparison with state-of-the-art polymer membranes. The research approach encompasses chemical vapor deposition growth of single- and few-atom thick 2D nanomaterials up to 4-inch wafer-scales, the optimization of 2D nanomaterials transfer on to apertures to make 2D nanomaterial membranes, followed by wet etching and transport studies to understand fundamental pore-forming and ion transport mechanisms. The research involves optimizing the manufacture of ultrathin membranes and maximizing water flow while retaining membrane integrity. This work further develops the instrumentation towards scale-up via roll-to-roll nanomanufacturing of the nanoporous membranes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.