Abstract

MXenes have attracted considerable attention due to their tunable surface chemistry, high electrical conductivity, and ease of solution processing, making them promising candidates for a wide array of applications. The inherent tendency of MXenes to degrade under environmental conditions constrains their compositional diversity and limits certain practical applications. Our computational study shows that degradation of defect-free Ti3C2Txis kinetically limited, whereas common defects markedly lower the activation barriers for water attack. Using ab initio molecular dynamics simulations (AIMD) combined with thermodynamic analysis, we show that titanium vacancies VTiact as active sites for the protonation of subsurface carbon atoms, weakening the bonds with and accelerating the release of adjacent Ti atoms. Targeted passivation of these sites by adsorbed metal cations (e.g., Li+, Na+, K+, and Mg2+) is predicted to effectively mitigate degradation by suppressing protonation and increasing the barrier for Ti oxidation. This stabilization arises from two synergistic effects: (i) electronic structure modification driven by a strong dipole moment, which markedly shifts the work function, and (ii) steric hindrance that limits water access to reactive defect sites. We also demonstrate that carbon vacancies VC significantly destabilize adjacent Ti atoms, lowering the energy barrier for the water attack reaction. The substitution of VC with electronegative species such as O or N does not significantly improve the stability of Ti3C2Tx, highlighting the detrimental role of any defects in the carbon sublattice. Because VC are typically inherited from the precursor phase and cannot be removed during post synthesis, controlling their concentration during Mn+1AXnphases synthesis is essential. Our thermodynamic analysis reveals that A-rich (e.g., Al-rich) synthesis conditions substantially increase the formation energy of VCand VNdefects in a large spectrum of Mn+1AXnphases, providing a generalizable strategy for defect suppression and improved durability of the resulting MXenes.

Department(s)

Chemistry

Keywords and Phrases

defects; degradation; DFT; molecular dynamics; MXenes; stability; Ti3C2Tx

International Standard Serial Number (ISSN)

1936-086X; 1936-0851

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2025 American Chemical Society, All rights reserved.

Publication Date

28 Oct 2025

PubMed ID

41085334

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