Large-scale
fabrication of MXene films is in high demand for various
applications, but it remains difficult to meet industrial requirements.
In this study, we develop a slot-die coating method for the preparation
of large-area MXene membranes. The technique allows the fabrication
of continuous and scalable coatings with a rapid coating speed of
6 mm s–1. The thickness can be readily controlled
from the nanometer scale to the micrometer scale, and the alignment
of the nanosheet is enhanced by the shear force of the slot-die head.
Molecular separation experiments employing a film with a thickness
of approximately 100 nm are performed. A nanofiltration performance
with water permeance of 190 LMH/bar and molecular weight cutoff of
269 Da is achieved, surpassing previously reported results obtained
using MXene-based nanofiltration membranes. The stability of the membrane
is highlighted by its nanofiltration performance of 30 days under
harsh oxidizing conditions, which is the longest operation ever achieved
for a 2D material-based membrane. The extraordinary stability of the
film suggests its high potential for industrial and practical applications.
The antioxidizing phenomena can be attributed to self-protection of
the MXene surface by adsorbed organic molecules, which are particularly
stabilized with positively charged molecules via chemisorption.
Solution-based processing of two-dimensional (2D) nanomaterials is highly desirable, especially for the low-temperature large-area fabrication of flexible multifunctional devices. MXenes, an emerging family of 2D materials composed of transition metal carbides, carbonitrides, or nitrides, provide excellent electrical and electrochemical properties through aqueous processing. Here, we further expand the horizon of MXene processing by introducing a polymeric superdispersant for MXene nanosheets. Segmented anchor-spacer structures of a comb-type polymer, polycarboxylate ether (PCE), provide polymer grafting–like steric spacings over the van der Waals range of MXene surfaces, thereby reducing the colloidal interactions by the order of 10
3
, regardless of solvent. An unprecedented broad dispersibility window for Ti
3
C
2
T
x
MXene, covering polar, nonpolar, and even ionic solvents, was achieved. Furthermore, close PCE entanglements in MXene@PCE composite films resulted in highly robust properties upon prolonged mechanical and humidity stresses.
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