Synthesis of two-dimensional carbide Mo2CTx MXene by hydrothermal etching with fluorides and its thermal stability

In this study, highly pure Mo 2 CT x MXene was successfully synthesized from Mo 2 Ga 2 C by etching in hydrothermal conditions for 24 h at 140–180°C. The etching solutions were lithium fluoride (LiF), sodium fluoride (NaF), potassium fluoride (KF) or ammonium fluoride (NH 4 F) mixed with hydrochloric acid (HCl). The temperature to obtain pure Mo 2 CT x MXene in NH 4 F + HCl solution was 140°C, lower than that in other etching solutions. The thickness of as-prepared monolayer Mo 2 CT x nanosheet was measured to be 1.5 ± 0.3 nm by atomic force microscope. From thermogravimetry and differential thermal analysis, Mo 2 CT x MXene was found to be stable in argon atmosphere at a temperature of up to 500°C. As the temperature increased, Mo 2 CT x MXene gradually transformed, and β-Mo 2 C/MoC/Mo 3 C 2 was eventually formed to coexist with Mo 2 CT x MXene at 700°C. In air atmosphere, Mo 2 CT x MXene was stable at 200°C. At 590°C, Mo 2 CT x MXene was completely oxidized to MoO 3 .