Synthesis and formation mechanism of Ti3C2Clx MXene by molten salt method

Abstract

MXene is a novel two-dimensional nano material with exceptional performance, which can be applied in the fields of energy storage structural materials, optics, catalysis, and sensors etc. However, its synthesis is a challenge to date. From the perspective of environmental friendliness, the method of Lewis salt etching can effectively avoid the use of dangerous reagents and has been seen as a pollution-free economic approach. In this article ZnCl2 molten salt was chosen as corrosive agent to etch Ti3AlC2 MAX phase and investigated the synthesis mechanism of Ti3C2Clx MXene. The influence of main process factor, like raw materials, sintering temperature, and holding time on synthesis product were studied and discussed. The synthesis route was investigated by XRD and thermal analysis. SEM and TEM technology was used to analyze the microstructure and lattice of synthesis product. The results showed that the optimal process conditions: the molar ratio of raw materials was 1:6 (Ti3AlC2: ZnCl2), the synthesis temperature and holding time were 600～700 °C and 4 h, respectively. Ti3C2Clx MXene material prepared by this method has a complete layered structure and uniform composition, and its synthesis mechanism can be concluded to two steps: the first step was the reaction between Ti3AlC2 MAX phase and ZnCl2 to generate Ti3ZnC2 MAX phase; In the second step, the Ti3ZnC2 MAX phase reacted with the remaining ZnCl2 to generate Ti3C2Clx MXene material.