LAUSR

Abstract The oxidation of MXenes has aroused considerable interest and attention in recent years, which is closely related to the synthesis process and environmental stability. However, there still remain many issues unclear about the oxidation of MXenes including the exquisite observation of the atomic reactions, and the influences of oxidizing gas and layer numbers. By combining reactive force field (ReaxFF) molecular dynamics simulations and density functional theory (DFT) calculations, the oxidation characteristics and mechanism of MXenes have been investigated. Herein, the oxidation of MXenes preferentially begins with O2 adsorption on the surface Ti layers, inducing the lattice distortion of Ti layers and the fracture of Ti-C bonds. Without the constraint from Ti atoms, the free C atoms reassemble to generate carbon chains inside the sheet. Surprisingly, the chains could erupt out of the sheet although some obstruction would appear. As a result of the reformation of Ti-C bonds and the blocking of interstitial O atoms, a few chains would be stuck inside. Besides, the layer number has great effects on the oxidation kinetics. As the layer number increases, the adsorption of O2 becomes easier but the eruption of carbon chains becomes weaker. Our findings would be instructive in enhancing corrosion resistance of MXenes and the preparation of oxidized MXenes.