Microwave-assisted hydrothermal synthesis of Ti3C2Tx MXene: A sustainable and scalable approach using alkaline etchant

The present work demonstrates an enhanced method for synthesising titanium carbide (Ti3C2TX) MXene using an alkaline etchant to remove aluminium (Al) element from the ternary titanium metal carbide (Ti3AlC2) MAX phase. The synthesis process employs a microwave-assisted hydrothermal heating route, offering a fluorine-free and safer alternative to conventional etching techniques. This method achieved rapid heating within just 45 min at 180 degrees C, significantly reducing the etching time compared to traditional etching, which often requires similar to 2-3 days. The effects of different sodium hydroxide (NaOH) concentrations (5 to 30 M) on the etching process were analysed. X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy confirmed structural modifications, showing a reduction of peak intensities and the existence of functional groups on etched MXene's galleries, such as Ti-O, C=O, C-H, and O-H. These structural modifications indicated a successful Al removal. Raman's analysis further verified bond formation within the etched MXene, such as Ti-C and Ti-O/Ti-OH bonds. Morphological analysis revealed a well-aligned, layered structure with substantial interlayer spacing at higher NaOH concentrations (27.5 and 30 M), indicating the formation of 2D MXene sheets. Elemental analysis showed significant Al reduction, especially at 27.5 and 30 M etched MXene, with remaining amounts of 21.9 % and 0.46 %, respectively. The UV-Vis spectroscopy identified etched MXene possessed magnetic properties at lower NaOH concentrations (5 and 10 M) with the band gap energy from 2 to 2.5 eV. Meanwhile, the etched MXene at higher NaOH concentrations (20 to 30 M) behave semiconductor-like with the band gap energy from 1.30 to 1.60 eV, corroborating the surface functionalisation of the MXene galleries. The findings suggest that NaOH concentrations of 27.5 M are ideal for potential applications, as higher concentrations improve functional groups and interlayer spacing. Future work will optimise this synthesis method, offering a fast and scalable approach to creating MXene for use in catalysis and electronic applications.