Condition optimization for exfoliation of two dimensional titanium carbide (Ti₃C₂T<i> _x </i>)

Abstract

The new class of 2D MXene material exfoliated from transition metal carbides receives increasing research interest due to its extraordinary properties and high potential in energy and environmental applications. However, the exfoliation of Ti₃C₂T _x , a widely studied MXene, from its precursor Ti₃AlC₂ by chemical etching in HF solution remains to be optimized. This study investigated the optimum exfoliation condition through systematic evaluating potential effects of reaction parameters, including the weight ratio of Ti₃AlC₂ in HF solution, etching time, reaction temperature, repeating etching, and sonication, on the yield, purity, and structure of produced Ti₃C₂T _x . Results show that a high weight percentage (5 wt%) of Ti₃AlC₂ etching at 50 °C for 36 h produced highly exfoliated MXene material. Etching at lower weight percentages (0.6-2.5 wt%) of Ti₃AlC₂ resulted in observable byproduct (AlF₃). Degradation of MXene layers with AlF₃ enrichment was observed under prolonged etching or higher temperatures. Room temperature etching failed to exfoliate Ti₃AlC₂ and the repeated etching denatured the MXene material. Introduction of controlled sonication during the etching produced highly exfoliated MXene with minimum etching time, which can be a promising alternative for high quality MXene production.