Fabrication and thermal stability of NH4HF2-etched Ti3C2 MXene

MXene, a new family of 2D transition metal carbides and carbonitrides, has been proved to possess excellent electrical conductivity and hydrophilicity. In this work, a single-step method to produce the larger interplanar spacing 2D MXene Ti3C2 by etching Ti3AlC2 with NH4HF2 was demonstrated, and the optimal reaction conditions between Ti3AlC2 and NH4HF2 were systematically researched. The morphology and microstructure of samples were characterized by scanning electron smicroscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD). The thermal stability of Ti3C2 was investigated by the thermogravimetry (TG) and differential thermal analyzer (DTA). It was found that the lattice parameter c of obtained Ti3C2 was up to 24.9 angstrom, and the larger interplanar spacing Ti3C2 was more stable than the sample exfoliated by HF. The transition temperature in air from NH4HF2-etched Ti3C2 to anatase TiO2 thoroughly is more than 500 degrees C, and the multilayered structure of Ti3C2 could be well retained even afer 900 degrees C heat treatment, while the value of HF-etched Ti3C2 is less than 350 degrees C. This work is important for exploring a safe synthesis method and well understanding the thermal stability of 2D MXene materials.