Omniphobic Polymer/Graphene Oxide-Coated PVDF Membrane for Stable Membrane Distillation in Surfactant-Containing Seawater

Graphene oxide (GO) coatings can improve the stable operation of membrane distillation (MD) membranes in the presence of organic contaminants by enabling the transport of water vapor through narrow interlayer spacings. However, GO's intrinsic hydrophilicity requires complex, multistep functionalization to achieve antiwetting properties, posing scale-up challenges. Here, we demonstrate a scalable fabrication of omniphobic polymer-graphene oxide (OGO) coatings on commercial PVDF membranes via sequential slot-die coating of GO followed by dip-coating in a perfluoropolyether (PFPE) solution. A highly volatile solvent and self-limited deposition enables conformal PFPE formation (∼hundreds of nanometers thick) onto GO, suppressing wetting while maintaining vapor-selective pathways with minimal transport resistance. In direct contact MD, OGO membranes achieved >99.7% NaCl rejection and >15 LMH water flux during long-term operation, even with low-surface-tension feeds containing surfactants. This GO-PFPE coating method avoids elaborate GO modification and is readily scalable, providing a generalizable strategy for antiwetting, antifouling surfaces in water remediation.