Ionic liquids intercalation in titanium carbide MXenes: A first-principles investigation

Area of Science:

• Materials Science
• Computational Chemistry
• Electrochemistry

Background:

• Two-dimensional (2D) MXenes, particularly Ti3C2Tx, are promising for energy storage.
• Ionic liquids (ILs) offer tunable properties as electrolytes.
• Understanding IL-MXene interactions is crucial for optimizing electrochemical devices.

Purpose of the Study:

• Investigate the intercalation of specific ionic liquids into 2D Ti3C2Tx MXenes.
• Analyze the influence of surface termination and pore charge on intercalation geometry.
• Evaluate charge transfer using multiple population analysis models and identify reliable methods.

Main Methods:

• Density Functional Theory with Dispersion Correction (DFT-D) calculations.
• Simulation of ILs (Emim+ with TFSA-, FSA-, FTFSA- anions) intercalation.
• Exploration of neutral, negative, and positive Ti3C2Tx pore systems.
• Application and comparison of Hirshfeld, Hirshfeld-I, DDEC6, Bader, and VDD charge analysis models.

Main Results:

• Detailed geometries of IL intercalation within Ti3C2Tx were elucidated.
• DDEC6 and Hirshfeld-I charge models were recommended for accurate charge transfer estimation.
• Non-covalent interactions between cations/anions and MXene surfaces were visualized.
• The cation arrangement and anion type significantly influence IL intercalation.

Conclusions:

• Cation-MXene and anion-MXene interactions are key determinants of IL intercalation in MXenes.
• The choice of charge analysis model impacts the interpretation of electronic interactions.
• This study provides insights into designing advanced MXene-based electrochemical systems.