Making recyclable cell phone batteries a reality with MXenes

MXenes are a family of two-dimensional (2D) transition metal carbides and nitrides with excellent properties such as high electrical conductivity, optical transparency, good mechanical strength, and thermal stability. However, MXenes are prone to severe oxidative degradation relatively quickly, which rapidly degrades their performance and limits their usefulness in many environments.

Hossein Alijani, Ph.D. researcher with the new rust killer. Image credit: RMIT University

A recent study published in the journal Nature Communications focuses on this problem by exposing oxidized MXene films to very brief high-frequency electromechanical vibrations, effectively removing the oxide layer and restoring their electrical and electrochemical properties.

MXenes: Why are they important?

MXenes are a new class of two-dimensional (2D) materials that have attracted much attention due to their unique properties and potential applications in various fields. MXenes are derived from compounds known as MAX phases, a class of ternary carbides and nitrides.

MXenes have a wide range of properties that make them useful for a variety of applications, including energy storage, electromagnetic interference shielding, and water purification.

MXenes have been found to have high conductivity, making them suitable for use in electronic devices. They also have a large surface area, which can be useful for adsorption and catalysis.

In addition, MXenes are highly flexible and robust and exhibit high thermal stability. These properties make MXenes a promising material for applications in a variety of applications, including energy storage, electromagnetic interference shielding, and water purification. They are also being studied for biomedical applications such as tissue engineering and drug delivery.

Challenges and limitations associated with MXenes

MXenes have shown great potential in various applications; however, there are still significant challenges to be overcome for their widespread application. One of the main limitations of MXenes is their susceptibility to oxidative degradation when exposed to moist air or aqueous environments.

As a result, they degrade rapidly, which limits their applicability in many practical settings and when long-term operation is sought. Also, when an oxide layer forms on the surface of the material, it can only be removed by strong acids, which also damage MXenes.

Therefore, efforts should be made to extend the life of MXene to ensure its potential to become a reality. So far, efforts have focused on increasing the oxidative stability of MXenes by prolonging their oxidation dynamics during preliminary synthesis or later during storage. However, a simple and rapid method for the recovery and recovery of oxidized MXenes is still needed.

Highlights of the current study

The study was carried out using various Ti-based MXene samples synthesized by liquid exfoliation method. The samples were exposed to humid air or aqueous environments and their oxidative degradation was monitored for hours to days.

Oxides such as titanium dioxide (TiO2) on the surface of MXene samples was also analyzed using various characterization techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM).

To explore ways to extend the shelf life of MXenes, the researchers also evaluated various methods to improve the oxidative stability of the materials. This included storing the MXene samples in hermetically sealed containers at low temperatures, as well as using various chemical treatments and annealing processes to delay the oxidation kinetics.

The performance of these methods was evaluated by analyzing samples before and after treatment using these characterization methods. In addition, the team also attempted to recover and regenerate the oxidized MXenes using various acid treatments.

Conclusions and future perspective

The findings of the current study demonstrated a facile and rapid method for the recovery and recovery of oxidized MXenes. This method involves treating MXenes with a hydrazine hydrate solution, effectively reducing the oxide layer on the surface of the material.

As a result, the electrochemical performance and lifetime of MXenes are significantly improved. The researchers also found that the reconstituted MXenes retained their structural integrity and showed no signs of damage or degradation.

Looking to the future, this study opens up new possibilities for the use of MXenes in practical settings where a longer period of time is desired. The ability to recover and regenerate oxidized MXenes is a potential solution to the rapid action and shelf-life degradation that previously limited their utility.

The researchers also suggest that the method could be applied to other transition metal carbides and nitrides, which could further expand the potential applications of MXenes.

A word from the researchers

The surface oxide, which is rust, is difficult to remove, especially from this material, which is much, much thinner than a human hair.“said Hossein Alijani, co-author of the study.

Current oxidation reduction methods rely on a chemical coating, which limits the use of MXene in its natural form. In this work, we show that exposing an oxidized MXene film to high-frequency oscillations for just one minute removes rust from the film. This simple procedure allows to restore its electrical and electrochemical properties.

Hossein Alijani, co-author, Ph.D. Candidate, RMIT School of Engineering

Link

Ahmed, H. et al. (2023). Regeneration of Oxidized Two-Dimensional MXenes Using High-Frequency Nanoscale Electromechanical Vibration. Nature communications. Available at: https://doi.org/10.1038/s41467-022-34699-3

Source: RMIT University

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