Two-dimensional materials are crystals that have one or more layers, all atoms of which are located in the surface layer. This makes them highly chemically active and, as a result, easy to use as electrodes – devices that conduct electric current. However, the synthesis of two-dimensional materials requires expensive equipment, making them difficult to use on a mass scale.
The scientists from the Yuri Gagarin State Technical University of Saratov and the Institute of Solid State Chemistry and Mechanochemistry SB RAS made an attempt to solve this problem by proposing a new technology for producing MXenes – two-dimensional compounds consisting of titanium and carbon atoms and are used in energy storage electrodes. First, chemists obtained a precursor material that, in addition to titanium and carbon, contained aluminium atoms. The synthesis was carried out in a melt of potassium and sodium chloride salts at a temperature of 1,250 degrees Celsius (i.e., 250 degrees lower than during previous experiments). This made it possible to avoid oxidation of the material by atmospheric oxygen, and also facilitated the distribution of reagents in the melt at relatively low temperatures.
Afterwards, the scientists treated the compounds with aluminium for 24 hours using a mixture containing hydrochloric acid and fluorine salts (these operations were conducted at a temperature of 140 degrees Celsius). This allowed them to remove aluminium atoms and separate the two-dimensional layers of titanium carbide linked with them into thin flakes measuring thousandths of a millimetre. Finally, at the last stage of the experiment, the chemists applied a suspension of these flakes to a copper substrate and dried it, obtaining a flexible film from the synthesised compound.
Measurements of the electrochemical capacitance of the materials, i.e., their ability to accumulate an electric charge, have demonstrated values that are twice as high as those of the industrial analogues. “Our work demonstrates that high-quality MXenes can be produced in a laboratory with standard equipment. We have proposed a scalable synthesis of a promising material for electrochemical energy storage, and we will soon complete work on the dielectric response, or the reaction of solids to alternating current, in composite materials using MXenes,” Nikolay Gorshkov, leader of the study and candidate of technical sciences, is quoted as saying by the Russian Science Foundation.
