Unraveling the Thermal Properties of (Mo_2/3Er_1/3)₂C i-MXene: Phase Changes and Surface Chemistry

Quaternary i-MAX phases, atomically layered solids with the chemical formula (M’_2/3M”_1/3)_2​AlC, were recently discovered and have since garnered significant attention for their magnetic properties, piezoelectric characteristics, and more. Few studies have explored the preparation of i-MXenes using exfoliation and delamination techniques, with specific samples exhibiting the highest capacitance values. Although their structural and magnetic properties have been examined, there remains a need for a deeper understanding of their thermal properties. To address this in this study, we prepared i-MAX phases using molybdenum as M1 and rare earth elements M2 as Er. These prepared materials were subsequently processed with the mild etching method to produce i-MXene. We analyzed i-MXenes, namely (Mo_2/3Er_1/3)₂C using XRD, XPS, Raman spectroscopy, SEM, EDS, TGA, and DSC to understand their fundamental properties and stability under thermal stress. From the XRD and Raman data, we observed that the solid-solution i-MXene shows that, along with Al, a certain percentage of the Er elements were also etched, as confirmed by the XPS and EDS profiles. Here, we provide detailed insight into the i-MXene by performing the TGA up to 1000°C and DSC up to 200°C under an inert atmosphere to understand its degradation behavior at elevated temperatures. The thermal behavior, including kinetic activity and phase change within this temperature range, indicates significant insights into surface terminations such as hydroxyl (-OH), oxygen (-O), fluoride (-F), and intercalated species in i-MXenes. Endothermic and exothermic peaks observed in the DSC measurement for i-MXenes in the 80 to 100°C range suggest that the material is experiencing structural changes with temperature. The findings provide insights into the thermal behavior and stability of these novel i-MXenes, contributing to the advancement of their use in various technological applications.