Two-dimensional Ti3C2Tx MXenes have demonstrated potential in applications such as optoelectronic devices. The thermal stability of these ultrathin films must be carefully considered due to ambient humidity, unavoidable heating caused by light absorption, current flow, or other hostile environmental conditions. Here, we use in-situ spectroscopic ellipsometry to study Ti3C2Tx MXenes oxidation and evaluate the resulting structures using atomic force microscopy. We demonstrate that after various heating treatments in a vacuum, degradation can be dramatically suppressed upon heating in ambient conditions. Contrary to conventional wisdom, our work demonstrates that upon proper thermal treatment, Ti3C2Tx MXene monolayers and single flakes are more thermally stable than their multilayer counterparts. We discuss how one can improve thin film stability through thermal drying in a vacuum and establish the appropriate conditions for each type of film. Density functional theory calculations elucidate possible reasons for the improved stability of monolayers. Our findings provide important design rules for Ti3C2Tx-based devices, which is very important for the further application of MXenes.

Ti3C2Tx MXene monolayers are more thermally stable than their multilayer films

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