Roll-To-Roll Fabricating Mene Membranes with Ordered Interlayer Distances For Molecule And Ion Separation

Application-oriented assembly of two-dimensional nanosheets with uniform nanochannels is critical for fabricating sophisticated, high-performance membranes for water treatment. However, fabricating the desired membranes by a simple, fast, and effective method is a challenge as most of the previous methods are based on batch processes rather than a continuous roll-to-roll process. Here, a simple Meyer rod-coating approach to continuously fabricate large-size and flat MXene membranes at a scale up to 5 m is introduced. This study demonstrated that a high MXene concentration, above 10 mg mL(-1), is critical in processability due to the desired viscosity, surface tension, and viscoelastic properties. The as-made MXene membranes show that shearing and solutal-Marangoni flow can considerably improve the ordering of the stacked MXene nanoflakes. Thus, the rod-coated MXene membranes demonstrate a smaller surface roughness and interlayer distance compared to the MXene membranes fabricated by the most commonly vacuum-assisted filtration. The rod-costed MXene membranes show superior performance in dye and mono/divalent cation separation. The proposed roll-to-roll Meyer rod-coating method can also be used to fabricate MXene-based composites, such as MXene/carbon nanotubes and MXene/polymer, using the inks containing high concentration MXene and other desired compositions. This roll-to-roll method will promote an industry-level fabrication and application of MXene-based membranes.

Automated summary

The application-oriented assembly of two-dimensional nanosheets with uniform nanochannels is crucial for fabricating advanced membranes for water treatment. In this study, a simple Meyer rod-coating approach is introduced to continuously fabricate large-size and flat MXene membranes. The fabricated MXene membranes show improved ordering and performance compared to traditional vacuum-assisted filtration methods. The proposed roll-to-roll Meyer rod-coating method also enables the fabrication of MXene-based composites.