Source Title: Researchers for the first time from the atomic scale reduction of MXenes oxidation kinetics
Recently, the team of Associate Professor Meng Xing, Key Laboratory of New Battery Physics and Technology of the Ministry of Education, College of Physics, Jilin University, has made important progress in the theoretical calculation of the oxidation behavior of
Two-Dimensional Transition Metal carbides/nitrides/carbon nitrides (MXenes), and the relevant results were published online in the German Applied Chemistry on June 14, 2023.
Because of its high conductivity and rich surface functional groups, MXenes is widely used in energy, electronic devices, biomedicine and other fields. However, MXenes easily degrades into
Transition Metal oxides in wet environments or aqueous solutions, which limits its application in various fields. Therefore, how to synthesize MXenes materials with high chemical stability is a key scientific problem to be solved urgently.
In the study, Meng's research team conducted an in-depth theoretical calculation study on the oxidation behavior of the super-large Mxenes-water system. By combining machine learning with first-principles calculations, the researchers achieved nanosecond molecular dynamics simulations with DFT accuracy, and for the first time reduced the kinetic process of MXenes oxidation from the atomic scale, revealing the nature of the exponential decay of MXenes oxidation rate observed experimentally. The oxidation mechanism of MXenes in wet environment or aqueous solution was elucidated.
The researchers developed A neural network potential function for the MXENes-water system, which performs well on the test set, with root-mean-square errors of 2.35meV/atom for energy and 0.083eV/ A for force compared to DFT calculations. The MD simulation based on the potential function is highly consistent with the AIMD simulation in the radial distribution function and the dynamic density property test. The MD simulation results of MXENes-water system show that the thicker the water layer, the more vertical hydrogen bonds per unit of water molecules, the more limited the movement of water molecules to the MXenes base surface, resulting in an increase in the average distance between the transition metal atoms and the oxygen atoms in water, and the MXenes oxidation rate decreases with the increase of the water layer thickness. At the same time, the oxidation of MXenes will release free protons, which will form a typical hydrated proton with water, thus binding the movement of water molecules, making the oxidation rate of MXenes decrease with the increase of time. The average distance between different types of transition metal atoms and oxygen atoms in water, as well as the probability of physical adsorption of water molecules on the MXenes base surface, demonstrate the existence of an oxide protective layer on the MXenes surface.
These important findings provide theoretical guidance for the synthesis of highly stable MXenes materials.
