In Situ and Quasi–In Situ Raman Spectroscopy Analysis of the Temperature‐Dependent Evolution in Structure and Surface Groups of Ti 3 C 2 T x MXene

ABSTRACT Two‐dimensional (2D) transition metal carbides and nitrides (MXenes) have attracted considerable attention due to their exceptional potential in electronics, electrochemical energy storage and conversion, optics, biomedicine, and sensing. However, their structural skeleton and surface terminations are highly sensitive to temperature, and thermally induced structural evolution can profoundly modify their physicochemical properties and device performance. Consequently, analytical methods capable of accurately identifying and continuously monitoring the structural dynamics of MXenes are urgently required. Within this context, Raman spectroscopy has emerged as a powerful and accessible technique for sensitively probing MXene lattice vibrations and surface chemistry. Using Ti 3 C 2 T x as a model MXene, this study employs in situ and quasi–in situ Raman spectroscopy to systematically elucidate its temperature‐dependent structural evolution during thermal annealing. The Raman response captures a series of sequential transformations triggered by heating, including interlayer water removal, depletion of –OH terminations accompanied by the growth of =O groups, loss of –F terminations, formation of C–C bonds, lattice oxidation, and eventual TiO 2 formation. By tracking the shifts and intensity variations of characteristic Raman modes, distinct structural states across the thermal evolution pathway are resolved, enabling the construction of a comprehensive spectral fingerprint that delineates the entire heat‐driven transformation process. These in situ Raman insights not only deepen the fundamental understanding of MXene thermal stability and structural evolution mechanisms but also provide an essential diagnostic basis and practical guidance for optimizing their performance and stability in electronic devices, electrochemical energy‐storage systems, and sensing applications.