A first-principles study of multilayer Ti₃C₂T MXene model.

Area of Science:

• Materials Science
• Computational Chemistry
• Surface Science

Background:

• Two-dimensional materials like MXenes are promising for energy storage.
• Understanding multilayer structures is crucial for optimizing MXene properties.
• Previous models may not fully capture the complexity of etched MXene.

Purpose of the Study:

• To propose and validate a realistic multilayer Ti3C2Tx model.
• To investigate the structural and electronic properties of MXene with varying hydrofluoric acid (HF) concentrations.
• To establish a baseline model for future MXene research.

Main Methods:

• Construction of various multilayer Ti3C2Tx structures with different HF concentrations (5, 10, 48 wt%).
• Theoretical calculations of d-spacing, X-ray diffraction (XRD) spectra, and adhesion energy.
• Analysis of interlayer interactions using Crystal Orbital Hamilton Population (COHP).

Main Results:

• The proposed ternary mixed O/OH/F-terminated multilayer models align with experimental data (d-spacing, XRD, adhesion energy).
• Both uniform and mixed-terminated multilayer Ti3C2Tx exhibit metallic properties.
• OH-rich surfaces show stronger interlayer interactions due to hydrogen bonding, while stronger HF etching leads to lower adhesion energy.

Conclusions:

• The developed multilayer Ti3C2Tx model provides a realistic representation of etched MXenes.
• Stronger HF etching facilitates exfoliation into monolayer sheets due to reduced adhesion energy.
• This work offers fundamental insights for advancing hydrogen and ion storage applications in MXenes.