Hydration of Ti3C2Tx MXene: An Interstratification Process with Major Implications on Physical Properties

The MXenes, among which Ti3C2Tx is the most studied, are a large family of two-dimensional materials with proven potential in a variety of application fields (e.g., energy storage and conversion, water purification, electromagnetic interference shielding, humidity sensor, etc.). For most of these applications, the properties of MXenes depend, at least partly, on their water sorption ability and on the induced structural swelling, which is commonly considered a stepwise process, like in claylike materials. In the present study, we rather evidence the systematic coexistence of different hydrates in MXene interstratified crystals. Hydration heterogeneity and related structure disorder are described from the quantitative analysis of X-ray diffraction data. This specific methodological approach allows disentangling the complex interstratification and rationalizing the prediction of MXene electrical properties. The widespread use of this approach paves the way for a systematic and thorough determination of MXene structure, including order-disorder, and thus for grasping the influence of structural disorder (hydration heterogeneity) on a large number of MXene physical properties (e.g., optical transparency, capacitance). Deciphering this complex structural disorder is also essential in the design of new MXene-based materials for a variety of applications (supercapacitors, batteries, water treatment, etc.).