Scalable Production and Covalent Functionalization of WS 2 Nanosheets for Membrane Fabrication and Ion Separation

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Abstract
Transition metal dichalcogenide (TMD) membranes offer a promising solution to freshwater scarcity by desalinating seawater through ion blocking. However, research has largely focused on MoS2 due to its efficient exfoliation via n-butyl lithium intercalation, unlike other TMDs. Here, we report scalable production of WS2 nanosheets by increasing the Li+ intercalation driving force (increasing current density up to 10 mA g-1 and decreasing cutoff voltage down to 0.7 V) of the electrochemical intercalation method. WS2 membranes were then fabricated by organohalide functionalization followed by vacuum filtration. The resulting membranes exhibit a high rejection rate of up to 90% for divalent and trivalent cations. The selectivity for monovalent/divalent and monovalent/trivalent cations reaches up to 8.7 and 9.9, respectively, in both single and binary cation solutions. Theoretical calculations reveal that the improved rejection rates of divalent and trivalent cations compared to those of monovalent cations originate from the stronger binding preferences of monovalent cations with functionalized WS2 membranes.
Funding Information
  • Research Grants Council, University Grants Committee (11308923)
  • Research Grants Council, University Grants Committee (11309425)
  • Research Grants Council, University Grants Committee (11309824)
  • Research Grants Council, University Grants Committee (C1003-23Y)
  • Innovation and Technology Commission (ITS/192/23)
  • Junior Research Fellow Scheme (JRFS2526-1S12)

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