The photo is sourced from pme.uchicago.edu
MXenes are two-dimensional materials that can include metals, nonmetals, nitrogen and carbon. As a rule, MXenes are obtained by etching toxic chemicals, although this method has a number of drawbacks: the reaction must be carried out at high temperatures, after which hazardous waste must be disposed of and MXenes must be purified by removing impurities formed during the etching process.
A more environmentally friendly alternative has been proposed by scientists from the Institute of Solution Chemistry RAS, who used plasma – an ionised gas at a high temperature – based on carbon tetrachloride to obtain MXenes. At room temperature, this compound takes the form of a liquid that begins to boil and turn into gas at a temperature of 76.5 degrees Celsius.
The researchers placed two titanium wires in this medium, using one wire as a cathode (a positively charged electrode) and the other as an anode (a negatively charged electrode). A short electrical discharge was then passed through them, creating a plasma directed from one wire to the other. Titanium would melt near the plasma, forming two-dimensional MXene structures in the solution. The authors dried the solution at room temperature, obtaining MXene powder as a result. Analysis of its chemical composition showed that the MXenes synthesised in that way do not contain oxide impurities that would worsen the electromagnetic properties of the materials.
The chief advantage of the new method is that the composition of MXenes can be easily varied by replacing the electrode material with another metal (such as molybdenum, chromium or tungsten). This will make it possible to obtain materials with specified target properties, be they electrical, magnetic, optical or biological. At the same time, this method is easily scalable and does not require the disposal of byproducts.
“The proposed method is the easiest way to synthesise MXenes without impurities. In the future, we plan to use single-stage processes to obtain membrane composites containing MXenes, which can be used as compact desalination units for saltwater,” Nikolai Sirotkin, one of the authors of the study and candidate of chemical sciences, is quoted as saying by the Russian Science Foundation.
