Slowing the breakdown of aqueous MXenes in colloidal solutions

Due to their beneficial properties, MXenes have been proven as primary substances for use in various applications. However, these materials face problems when it comes to degradation.

Study: Combination of high pH and an antioxidant improves the chemical stability of two-dimensional transition metal carbides and carbonitrides (MXenes) in aqueous colloidal solutions† Image Credit: Africa Studio/Shutterstock.com

To solve this problem, a paper published in the journal Inorganic Chemistry presents an innovative technique to improve the chemical-based stability of the MXenes.

MXenes – what exactly are they?

MXenes have been widely studied over the past decade for their remarkable electrical, thermal, optical and mechanical properties. These 2-dimensional configurations of metal carbides and nitrides are often synthesized by hydrous chemical etching through their MAX phase precursors.

MXenes are synthesized in colloidal form in aqueous environments, which is also a popular storage method because these compounds have a strong affinity for water.

The uniqueness of MXenes

MXenes’ interesting mix of high electrical conductivity and hydrophilicity (strong affinity for water) and their ability to tolerate intercalants make them extremely useful for applications such as energy production and storage, water purification, sensing and shielding from electromagnetic interference.

Nevertheless, little is known about the chemical nature of these 2D materials, much less about the effect of variables such as temperature, pH and solution concentration on their reactivity.

Hydrolysis – The main contributor to the breakdown of MXene

Previous research has shown that hydrolysis is the primary process contributing to the degradation of MXene in aqueous solutions. It has also been established that the surrounding pH value can significantly influence the rate of hydrolysis.

Although only a few articles have been published on the subject, the rapid degradation of MXene in base media has been recorded and interpreted quite thoroughly, mainly the reaction between MXene and OH.

These and many other conflicting results regarding the chemical stability of Mxene at the colloidal stage require further investigation. Direct identification of the byproducts of Mxene reactions provides a comprehensive technique to analyze the responsiveness of these materials in this regard.

Basis of Mxenes .’s current research

In this work, the researchers used a direct examination of the byproducts of the gas-based reaction using Raman spectroscopy and gas chromatography to evaluate the chemical stability of Mxenes over time in aqueous solutions at varying starting pH values.

The study is further complemented by observing the Mxene concentration in the solution via UV-vis spectroscopy, along with electrical conductivity tests of Mxene plates and post-mortem examination of the degradation associated with solid Mxene products using X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy.

To reduce the effects of the counterions, which can inhibit the effects of pH when an alkaline or acidic solution is used, the team used an electrolyte that was pH-inert.

The researchers devised a synergistic method to suppress the degradation of MXene and extend its life by efficiently blocking hydrolysis and oxidation.

The team expected the findings would help design better storage techniques for aqueous MXene solutions and lead to a better understanding of basic chemical processes.

Results of the study

The impact of the pH of the aqueous solution on the degradation of MXene was investigated by gas chromatography and Raman spectroscopy for evolved gases, as well as visual observations and classification of solid reactive products using X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy.

The team emphasized that depending on the specific pH level, the breakdown of MXene produces layered metalates. It was revealed through the experiment that the degradation of MXenes in aqueous solution is inhibited under alkaline conditions, mainly due to a slower hydrolysis rate.

It was suggested that combining a basic microenvironment with the introduction of a specific antioxidant is an efficient technique to inhibit both the hydrolysis and oxidation of MXenes in aqueous solutions, thereby extending their lifespan. The life extension would be longer than would have been possible with either strategy individually.

The team concluded that these discoveries are critical to a deeper understanding of the chemistry associated with MXenes and equally crucial to the formulation of improved storage techniques.

Reference

Huang, S., and Mochalin, V. (2022). Combination of high pH and an antioxidant improves the chemical stability of two-dimensional transition metal carbides and carbonitrides (MXenes) in aqueous colloidal solutions. Inorganic ChemistryAvailable at: https://doi.org/10.1021/acs.inorgchem.2c00537

Disclaimer: The views expressed here are those of the author expressed in a personal capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork, the owner and operator of this website. This disclaimer is part of the Requirements from using this website.

#Slowing #breakdown #aqueous #MXenes #colloidal #solutions

Leave a Comment

Your email address will not be published. Required fields are marked *