Fourier-Transform Infrared Spectral Library of MXenes

Fourier-transform infrared (FTIR) spectroscopy characterization is a powerful and easy-to-use technique frequently employed for the characterization and fingerprinting of materials. Although MXenes are a large and fastest growing family of inorganic 2D materials, the lack of systematic FTIR spectroscopy studies hinders its application to MXenes and often leads to misinterpretation of the results. In this study, we report experimental and calculated FTIR spectra of 12 most typical carbide and carbonitride MXenes with different compositions (5 transition metals) and all four basic structures, including Ti₂CT _<i>x</i> , Nb₂CT _<i>x</i> , Mo₂CT _<i>x</i> , V₂CT _<i>x</i> , Ti₃C₂T _<i>x</i> , Ti₃CNT _<i>x</i> , Mo₂TiC₂T _<i>x</i> , Mo₂Ti₂C₃T _<i>x</i> , Nb₄C₃T _<i>x</i> , V₄C₃T _<i>x</i> , Ta₄C₃T _<i>x</i> , and Mo₄VC₄T _<i>x</i> . The measurements were performed on delaminated MXene flakes incorporated in KBr pellets in the 4000-400 cm^-1 range. We provide detailed instructions for sample preparation, data collection, and interpretation of FTIR spectra of MXenes. Background correction and spectra smoothing are applied to obtain clear FTIR peaks corresponding to bond vibrations in MXenes. Density functional theory calculations were used for the precise assignment of all characteristic FTIR peaks and an in-depth analysis of the vibration modes. This work aims to provide the 2D material community with the FTIR spectroscopy technique as a reliable method for identifying and analyzing MXenes.