Interesting possibilities with amorphous MXene materials

(Nanowerk Highlights) Scientists have recently discovered a new class of amorphous nanomaterials which are made by introducing a disordered arrangement of atoms. These materials show excellent performance in catalysis, energy storage and mechanics. In a recent Perspectives article on Advanced Materials (“Amorphous MXene Opens New Perspectives”), scientists explore the possibilities of amorphous MXene, specific types of 2D materials, and their potential applications.

Amorphous materials – materials that do not have a long-term regular structure – have interesting physical and functional properties, opening up great opportunities for scientific discoveries. Amorphous 2D materials, in particular, are of interest for future advanced technologies due to the properties of 2D structures and disordered arrangement of atoms.

Examples of these materials include amorphous graphene, transition metal dichalcogenide, boron phosphide, and boron nitride, all of which have unique properties and applications in electronics, optoelectronics, energy storage, and electrocatalysts.

Recently, a new family of 2D materials called MXenes has received attention. These materials consist of transition metal carbides, nitrides, and carbonitrides, and have exhibited outstanding properties such as high electrical conductivity, hydrophilic properties, and large surface areas. MXene has been used as a precursor to prepare amorphous transition metal oxides.

However, amorphous MXene itself has not been reported. These materials can have more defects and reactive sites due to their disordered atomic arrangement, which potentially gives them better chemical activity and conductivity compared to crystalline materials. This makes amorphous MXenes a promising candidate for enhancing energy storage and transformation applications.

Proposed Method for Creating and Applying Amorphous MXene

When it comes to preparing amorphous MXenes, the strong bonds in their structure make it difficult to achieve using traditional synthesis methods. Here, the authors suggest several possible approaches to making these materials. Possible methods of synthesis and application of amorphous MXene. (Reprinted with permission by Wiley-VCH Verlag)

High energy ball milling, a solid state non-equilibrium process, has been used to prepare nanocrystalline or amorphous materials. This method has been successful in producing amorphous boron nitride, for example. However, using this technique for MXenes requires isolating air and adding a grinding agent, which can be experimentally challenging.

Another option is to use an amorphous precursor as an intermediate product in the 2D crystal formation process. Inhibiting the transformation of the amorphous state into a long-term ordered state is the key to making amorphous materials. Methods such as PLD, sputtering, and hydrothermal reactions, which have been used for other 2D materials, are rarely applied to MXene, making it difficult to use these methods as a reference.

For MXenes, exfoliation is the most common method of making them. However, it is difficult to obtain amorphous MXene by etching after preparing disordered MAX. One alternative way to make MXenes amorphous is to block the arrangement of the atomic sequences during the exfoliation process. Rapid heating during exfoliation can help achieve this, as the sudden expansion of the gas can lead to the formation of defects on the MXene surface, driving lattice distortion.

Another promising approach to fabricating 2D amorphous nanomaterials is to prevent the arrangement of atoms of 2D nanocrystalline materials without affecting their 2D shape. This can be achieved by continuously intercalating and deintercalating electrons, ions or molecules from the crystal lattice, leading to the collapse of the crystal structure. Subjecting 2D crystalline MXene to electrical treatment, for example, could promote the transformation of the crystals into amorphous solids.

Supercritical carbon dioxide (sc-CO2) is another promising substance for making amorphous MXene. Its physical properties can be easily controlled, and have potential applications in the design and manufacture of 2D materials. The effects of pressure and temperature on exfoliation and the reversible crystal-to-amorphous phase transition in MXenes deserve further exploration.

In addition to experiments, theoretical investigations of amorphous MXenes can help researchers better understand this material. More efforts should be made to theoretically clarify their growth mechanisms in the future. Diverse modeling methods should be further developed, facilitating theoretical research on amorphous MXene.

Conclusion

Current research on amorphous materials focuses on applications for catalysis and energy storage. The catalytic activity of MXenes originates from exposed metal sites on defects and edges. Amorphous MXene can expose more metal sites to external fields such as heat, light and electricity, increasing their catalytic activity. This also increases their capacitance, making them potentially useful in energy storage and transformation applications.

Although the scope of application for amorphous MXene is still limited, its outstanding performance in energy storage and transformation has been demonstrated. Combining amorphous MXene with other functional nanomaterials, such as graphene/amorphous-MXenes hybrids, can produce materials with high strength and toughness. The unique structure and properties of 2D amorphous MXenes can also reveal unexpected properties. In conclusion, the development of amorphous MXenes could be a powerful approach to fabricate new multifunctional 2D materials for a sustainable future. By

Michael
Berger
–

Michael is the author of three books by the Royal Society of Chemistry:
Nano-Society: Pushing the Boundaries of Technology,
Nanotechnology: A Small FutureAnd
Nanoengineering: Skills and Tools for Making Technology Invisible
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