Atomistic Insights of Ti-Based MXenes Thermal Decomposition and Transformation to Carbon-Supported Ti-O Phases for Energy Applications

Ti-O phases combined with carbon materials are attractive for applications in energy storage, photocatalysis, and gas sensing. The oxidation of Ti-based MXenes at high temperatures has been proposed as an effective synthesis method for carbon-supported anatase and rutile TiO2. Here, the thermal degradation and phase transformation of Ti3C2T2 (T = O or OH) under vacuum, air, and water vapor environments are investigated using reactive molecular dynamics simulations. Ti3C2(OH)2 is most stable under vacuum and water vapor, and is least stable in air. In contrast, Ti3C2O2 shows the lowest stability in air. In the air environment, anatase and rutile TiO2 phases are found regardless of the surface termination, while in water vapor, the water molecules disrupt the formation of a distinct phase. Under vacuum, we observe the formation of rock-salt TiO and present a comprehensive analysis of its transformation. The phase transformation temperatures for Ti3C2O2 are 700, 600, and 700 K for vacuum, air, and water vapor environments, respectively. Ti3C2(OH)2 showed phase stability up to 1100, 600, and 900 K under vacuum, air, and water vapor environments, respectively. Our comprehensive atomistic analysis provides detailed descriptions of the thermal degradation process and phase transformation of Ti3C2T2, which helps to understand the nanoscale aspects of the experimental work.