hydroxide anions react with the layers of Al in this technique, causing the Al to be

oxidized. Further, hydroxyl or oxygen radicals were formed with titanium atoms, after

dissolving the Al(OH)3 hydroxides in alkali. The procedure, on the other hand, allows

the production of new Al hydroxides, which are further confined in the titanium layer

and does not react with hydroxyl ion anymore. The ease of reaction has been carried

out by using sodium hydroxide and varying the temperature of the hydrothermal in

an argon atmosphere. In this method, more hydroxyl and oxygen ions were found

in the MXenes than in the HF etching technique, which further enhances the overall

activity.

15.2.3 Electrochemical Synthesis

Yang et al. proposed the first electrochemical approach for delamination of Ti3C2 in a

binary aqueous electrolyte without the need of F in 2018. They used titanium alu­

minum carbide as the cathode and anode in a two-electrode setup. Only the anode

went through the etching procedure, yielding Ti3C2Tx. They utilized a pH-balanced

mixture of 1M NH4Cl and 0.2M tetramethylammonium hydroxide (TMAOH) to avoid

etching solely on the surface [11] which further helps in the deeper reaching of

electrolytes towards the layer of anode [7]. The bulk anode was gradually delaminated

using a low voltage of 5 V. To make individual sheets of Ti3C2Tx, the sediment and

suspended powders of Ti3C2Tx were crushed and put into a 25% weight/weight

tetramethylammonium hydroxide solution. The electrical conductivity of the MXenes

generated was comparable to that of those synthesized using HF or HCl/LiF [7].

However, in terms of overall etching yield, the electrochemical approach looks to be

the most promising, as up to 60% of the bulk material can be converted into

Ti3C2Tx [12].

15.2.4 In-situ Polymerization

By using monomers, initiators, and curing agents via a wet approach to the MXene

nanosheets, in-situ polymerization can be done and from this MXene can be evenly

distributed throughout the polymer hosts. The blending can significantly improve the

dispersion of MXene within the polymer matrix. The said protocol is widely used to

produce MXene-contained polymer nanocomposites. In the composites, the polymers

are thermosetting polymers containing cyclic or heterocyclic units or linear macro­

molecules, which can be polymerized in mild conditions [13]. Wang et al. reported

in-situ blending of Ti3C2Tx/epoxy resin nanocomposites [14]. Polyaniline (PANI),

polythiophene (PT), PEDOT and/or its derivatives, polydopamine (PDA), polypyrrole

(PPy), and other complex cyclopolymers usually can also be polymerized in-situ for

preparing MXene/in-situ polymerization polymer nanocomposites to be applied as

electrodes, catalysis, shielding functional materials, and other purposes. Qin et al. [15]

have used the pyrrole and MXene component to synthesize the MXene/PPy via the

electrodeposition technique. Further, in-situ polymerization techniques have been used

by Wang et al. to produce the Ti3C2Tx/ PDA composite [16]; similar protocols have been

used by Tong et al. [17] to synthesize the Ti3C2Tx/PPy composite. In-situ polymerization

mixing improved MXene dispersion in polymers strengthened the interaction between

MXene and the polymer matrix and improved the polymer’s thermal, mechanical, and

electrical properties.

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