Water-Mediated Ion Selectivity in 2D MXene Channels
Yuan Zhang1, Ming Chen2, Teng Zhang1
1Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States.
Journal of the American Chemical Society
|July 1, 2026
Summary
Water confined in 2D materials shows unique ion transport. Ti3C2Tx MXene nanosheets allow precise control over ion flow, enabling new designs for water desalination and separation technologies.
Area of Science:
- Nanofluidics and Materials Science
- Surface Chemistry and Water Behavior
- Ion Transport Mechanisms
Background:
- Confined water at the Ångström scale exhibits distinct properties compared to bulk water.
- Understanding ion transport in nanofluidic systems is crucial for natural and engineered applications.
- Existing models for aqueous ion transport are insufficient under extreme confinement.
Purpose of the Study:
- To investigate the fundamental mechanisms of selective ion transport mediated by confined water.
- To explore the use of 2D Ti3C2Tx MXene nanosheets as a platform for tuning ion transport.
- To establish design principles for advanced nanofluidic devices.
Main Methods:
- Utilized 2D Ti3C2Tx MXene nanosheets with controlled interlayer spacing (0.9-5.0 Å), surface terminations, and electrode potentials.
- Performed experimental measurements including ion permeation, spatial secondary-ion mass spectrometry, and Fourier transform infrared spectroscopy.
- Conducted molecular dynamics simulations to analyze water reorganization and ion-MXene interactions.
Main Results:
- Ultranarrow confinement reorganizes water structure and imposes ion-specific dehydration penalties.
- Li+ permeation in horizontally aligned Ti3C2Tx channels was significantly faster (2 orders of magnitude) than in vertically aligned membranes.
- Electrochemical surface charge modulation effectively regulated ion selectivity.
Conclusions:
- Confined water, surface chemistry, and energetics define a transport regime beyond classical diffusion.
- Ti3C2Tx MXene platforms offer tunable ion transport for various applications.
- Findings provide design principles for artificial ion channels and high-performance membranes for separation and desalination.
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