Micro-Structure and Dielectric Properties of Ti3C2Tx MXene after Annealing Treatment under Inert Gases

At present, the rapid development of electronic devices such as batteries, sensors, capacitors and so on is creating a huge demand for lightweight materials with a designed structure and function. Ti3C2Tx MXene, a lightweight two-dimensional (2D) nanomaterial with excellent electronic properties, has been favored in this field. In this work, Ti3C2Tx MXene was annealed under an inert gas (N2, Ar and CO2) atmosphere to design the crystal structure and interface of the nanosheets, and then the modified nanosheets with specific changes in dielectric properties were obtained. Among them, the key temperature points (100 °C, 300 °C, 500 °C and 800 °C) in the thermogravimetric (TG) test under an air atmosphere were used as the annealing temperature. When annealing under an air atmosphere, with the increase in temperature, the Ti layer gradually oxidized and evaporated, and the original two-dimensional structure was partly destroyed with some of the C atoms reacting with O2 to form CO2. In the inert gas atmosphere, however, the 2D structure is preserved, except that the surface end groups and layer spacing are changed. In addition, some N element doping was introduced into the nanosheets after N2 atmosphere treatment, which changed the original lattice structure. After the Ar atmosphere treatment, some Ti atoms on the surface were oxidized in situ to form TiO2 grains with different crystal forms, which increased the interfacial area. The C-TiO2 structure of the nanosheets was more complete after treatment with the CO2 atmosphere. All the nanosheets after heat treatment with an inert gas atmosphere retained the characteristic morphology of 2D materials, and different changes in the micro-structure caused changes in dielectric properties, thereby meeting the needs of 2D nanomaterials Ti3C2Tx MXene in different scenarios.