Condition optimization for exfoliation of two dimensional titanium carbide (Ti₃C₂T _x )

Abstract

The new class of 2D MXene material exfoliated from transition metal carbides receives increasing research interest due to its extraordinary properties and high potential in energy and environmental applications. However, the exfoliation of TiCT , a widely studied MXene, from its precursor TiAlC by chemical etching in HF solution remains to be optimized. This study investigated the optimum exfoliation condition through systematic evaluating potential effects of reaction parameters, including the weight ratio of TiAlC in HF solution, etching time, reaction temperature, repeating etching, and sonication, on the yield, purity, and structure of produced TiCT . Results show that a high weight percentage (5 wt%) of TiAlC etching at 50 °C for 36 h produced highly exfoliated MXene material. Etching at lower weight percentages (0.6-2.5 wt%) of TiAlC resulted in observable byproduct (AlF). Degradation of MXene layers with AlF enrichment was observed under prolonged etching or higher temperatures. Room temperature etching failed to exfoliate TiAlC and the repeated etching denatured the MXene material. Introduction of controlled sonication during the etching produced highly exfoliated MXene with minimum etching time, which can be a promising alternative for high quality MXene production.

Dispersibility and Photochemical Stability of Delaminated MXene Flakes in Water

“…The formation of 1 O 2 does not involve electron transfer. [61,63] Our results indicated that both UV and visible light could cause Ti 3 C 2 T x flakes to enter an excited state, promoting a shift from groundstate O 2 to 1 O 2 ; however, the HMH and KOH treatments (particularly the HMH treatment) may inhibit this process to some extent. Unlike the generation of 1 O 2 , the formation of O 2…”

“…[63] Self-combination with H 2 O serves as a major degradation process for O 2 − , which results in the formation of H 2 O 2 and the production of •OH. [61] The lower concentrations of O 2 − and •OH detected in the HMH-Ti 3 C 2 and KOH-Ti 3 C 2 suspensions could be due to the reduced electron donation caused by the adsorption of HMH molecules or K + ions. The differences in the ROS production between the three MXene flakes could be attributed to their different surface modifications and resulted in a photochemical stability sequence of HMH-Ti 3 C 2 > KOH-Ti 3 C 2 > H 2 O-Ti 3 C 2 , which is further discussed using DFT calculation and MD simulation in the following section.…”

“…Preparation of Ti 3 C 2 T x Flakes: The Ti 3 C 2 T x flakes were synthesized following the same method as described in our previous papers. [60,61] Briefly, the initial bulk Ti 3 C 2 T x powders were prepared by etching 5wt% MAX in 49% HF at 50 °C for 36 h. The obtained powders were washed with ultrapure water and centrifuged several times until the pH of the supernatant reached 5-6. The dispersion was filtrated through a PVDF membrane and then transferred to a vacuum desiccator overnight.…”

“…[60] Other XRD peaks at 18.4°, 27.9°, 35.1°, 43.3°, 52.6°, 57.4°, 60.5°, and 68.3° are also assigned to Ti 3 C 2 T x . [1,61] For the Raman spectra ( Figure 2C), the peaks at 205, 375, and 605 cm −1 are assigned to TiC vibrations. [1,54,59,62] The two bands at 1350 and 1570 cm −1 are assigned to the D and G bands of the carbon layer in the Ti 3 C 2 T x structure, respectively.…”

Synthesis and Regeneration of A MXene-Based Pollutant Adsorbent by Mechanochemical Methods

“…on the MXene surface (usually indicated as T x ) [23]. It can be realized with other etching agents (e.g., LiF + HCl conc., NH 4 F) and exfoliation methodologies (e.g., ultrasonication), but such a process can still be hardly scaled-up in a cost-effective manner due to large consumption of solvent and energy [24,25,26]. Therefore, a MC exfoliation process of the MAX phase has been also investigated by utilizing dimethyl-sulfoxide as solvent [27].…”