Temperature-dependent swelling transitions in MXene Ti₃C₂T.

Area of Science:

• Materials Science
• Nanotechnology
• Physical Chemistry

Background:

• Hydrophilic layered materials, such as MXenes, exhibit swelling behavior due to polar solvent penetration into their interlayer spaces, causing lattice expansion.
• Understanding MXene swelling is crucial for applications in energy storage and separation technologies, where interlayer spacing dictates ion and molecule transport.

Purpose of the Study:

• To investigate the temperature-dependent swelling behavior of MXene Ti3C2Tx in various polar solvents.
• To characterize the structural changes and phase transitions associated with MXene swelling in dimethyl sulfoxide (DMSO) and mixed H2O:DMSO solvents.

Main Methods:

• Synchrotron radiation X-ray diffraction was employed to study the temperature dependence of MXene Ti3C2Tx swelling.
• MXene samples were immersed in excess DMSO and a 2:1 H2O:DMSO solvent mixture, and their structural responses to heating were analyzed.

Main Results:

• An irreversible swelling transition was observed in MXenes immersed in excess DMSO upon heating (362-370 K), increasing the interlayer distance by 4.2 Å.
• This transition corresponds to a phase change from a one-layer DMSO solvate to a two-layer DMSO-MXene phase, which is stable after cooling.
• A similar transformation occurred at a lower temperature in a 2:1 H2O:DMSO mixture, involving water expulsion and formation of a pure two-layer DMSO-MXene phase.

Conclusions:

• MXenes undergo an irreversible, temperature-induced phase transition in DMSO, leading to a significant increase in interlayer spacing.
• This controlled change in interlayer distance via temperature cycling offers potential for tuning MXene properties in membrane and electrode applications.
• The findings highlight the importance of solvent choice and temperature in controlling MXene swelling for advanced material functionalities.