Hydration of Ti₃C₂T_x MXene: An Interstratification Process with Major Implications on Physical Properties

Abstract

The MXenes, among which Ti 3 C 2 T x is the most studied, are a large family of 2D 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, MXenes properties depend, at least partly, on their water sorption ability and on the induced structural swelling, which is commonly considered a stepwise process, like in clay-like 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…).

One MAX phase, different MXenes: A guideline to understand the crucial role of etching conditions on Ti3C2Tx surface chemistry

“…For the Ti 3 C 2 -HF10 powders, two (002) peaks can be clearly identified: a more intense one corresponding to a c parameter value of 19.9 Å and a less intense one corresponding to a c parameter value of 25.5 Å. The latter indicates the presence of some water between the sheets and is characteristic of the interstratification phenomenon observed in clay materials, as described in our previous work [46]. This hydration heterogeneity involves different layer-to-layer distances in the multilayer particle.…”

On a Two-Dimensional MoS2/Mo2CTx Hydrogen Evolution Catalyst Obtained by the Topotactic Sulfurization of Mo2CTx MXene

“…37 The broadening of the (002) peak, involving a lower crystallinity, is associated with an already reported interstratification phenomenon due to a distribution in the layer-to-layer distances. 38 Raman mode, where LA stands for a longitudinal acoustic phonon mode. The peak centered around 452 cm -1 is assigned to a second-order phonon peak (2LA) and a first-order mode.…”

Pristine Titanium Carbide MXene Films with Environmentally Stable Conductivity and Superior Mechanical Strength

“…The d ‐spacing is progressively evolved from 12.4 Å for original Ti 3 C 2 T x films (without acid processing step) to 10.4 Å for 0.1 m H + induced films (Figure a,b). This feature indicates that intercalated H 2 O in acid induced Ti 3 C 2 T x samples is gradually decreased as acid concentration increases, and the coexistence of region with intercalated H 2 O and region without intercalants is the reason for the progressive evolution in 002 diffraction peak, which was defined as an interstratification behavior . The mechanism underlying the less H 2 O in 0.1 m H + induced Ti 3 C 2 T x films is proposed as the difference in the amount of intercalated Li + .…”

“…Vacuum annealing treatment at 150 °C removed intercalated H 2 O in original films, in accordance with the change in d ‐spacing. Nevertheless, Li + between Ti 3 C 2 T x layers facilitates the reintercalation of H 2 O in high humidity environment . By contrast, the interlayer spacing in pristine Ti 3 C 2 T x films is not significantly influenced by both annealing and storing in 100% RH environment.…”