An investigation into the factors governing the oxidation of two-dimensional Ti3C2 MXene

Abstract

Two-dimensional (2D) transition metal carbides (MXenes) exhibit outstanding performances in many applications, such as energy storage, optoelectronics, and electrocatalysts. However, colloidal solutions of Ti₃C₂T_x MXene flakes deteriorate rapidly under ambient conditions due to the conversion of the titanium carbide to titanium dioxide. Here, we discuss the dominant factors influencing the rate of oxidation of Ti₃C₂T_x MXene flakes, and present guidelines for their storage with the aim of maintaining the intrinsic properties of the as-prepared material. The oxidation stability of the Ti₃C₂T_x flakes is dramatically improved in a system where water molecules and temperature were well-controlled. It was found that aqueous solutions of Ti₃C₂T_x MXene can be chemically stable for more than 39 weeks when the storage temperature (−80 °C) is sufficiently low to cease the oxidation processes. It was also found that if the Ti₃C₂T_x flakes are dispersed in ethanol, the degradation process can be significantly delayed even at 5 °C. Moreover, the oxidation stability of the Ti₃C₂T_x flakes is dramatically improved in both cases, even in the presence of oxygen-containing atmosphere. We demonstrate practical applications of our approach by employing Ti₃C₂T_x in a gas sensor showing that when oxidation is inhibited, the device can retain the original electrical properties after 5 weeks of storage.