Methylation sterically protects Ti3C2O2 MXene from thermal oxidation

Abstract

Two-dimensional MXenes possess exceptional properties but suffer from severe chemical instability under oxidizing and high-temperature conditions. In this work, we employ ReaxFF molecular dynamics simulations to demonstrate that methyl (–CH3) functionalization provides substantial protection for Ti3C2O2 MXene against thermal oxidation. While the pristine material undergoes active oxygen diffusion and massive structural degradation at 1000 K, the methylated system effectively preserves its lattice integrity over the simulated 2.0 ns trajectory under the same severe thermal stress. Atomistic analysis reveals that the methyl groups act as a robust interfacial steric shield, establishing a 5.0 Å exclusion zone that keeps atmospheric oxygen at a safe 6.2 Å distance from reactive Ti sites. Consequently, structural Ti–O bonds remain virtually unchanged, significantly suppressing early-stage oxide phase nucleation. Ultimately, surface methylation emerges as an effective passive strategy for enhancing the stability of MXenes under the high-temperature environments investigated in this study.