Two-Dimensional Carbides and Nitrides (MXenes) Enable New Energy Storage Technologies

X. Wang, Y. Gogotsi
Drexel University,
United States

Keywords: MXenes, 2D materials, Energy storage, Synthesis, Surface groups

Summary:

Two-dimensional (2D) materials with a thickness of a few nanometers or less can be used as single sheets, or as building blocks, due to their unique properties and ability to assemble into a variety of structures. Graphene is the best-known example, but several other elemental 2D materials (phosphorene, silicene, borophene, etc.) have been discovered. Numerous compounds, ranging from clays to boron nitride (BN) and transition metal dichalcogenides, have been produced as 2D sheets. By combining various 2D materials, unique combinations of properties can be achieved which are not available in any bulk material. The family of 2D transition metal carbides and nitrides (MXenes) has been expanding rapidly since the discovery of Ti3C2 in 2011 [1]. Approximately 30 different MXenes have been synthesized, and the structure and properties of numerous other MXenes have been predicted using density functional theory (DFT) calculations [2]. Moreover, the availability of solid solutions on M and X sites, control of surface terminations, and the discovery of ordered double-M MXenes (e.g., Mo2TiC2) offer the potential for synthesis of dozens of new distinct structures. This talk will focus on the synthesis of MXenes by selective etching of layered ceramic precursors, including various MAX phases. Delamination into single-layer 2D flakes and assembly into films and 3D structures, as well as their properties will be discussed. Synthesis-Structure-Properties of MXenes will be addressed on the example of Ti3C2. The versatile chemistry of the MXene family renders their properties tunable for a large variety of energy-related applications. Oxygen or hydroxyl- terminated Menes, such as Ti3C2O2, have been shown to have redox capable transition metals layers on the surface and offer a combination of high electronic conductivity with hydrophilicity, as well as fast ionic transport. This, among many other advantageous properties, makes the material family promising candidates for energy storage and related electrochemical applications [2,3]. But applications in plasmonics, electrocatalysis, biosensors, water purification/ desalination and other fields are equally exciting. References 1. M. Naguib, M. Kurtoglu, V. Presser, J. Lu, J. Niu, M. Heon, L. Hultman, Y. Gogotsi and M. W. Barsoum. Two-Dimensional Nanocrystals Produced by Exfoliation of Ti3AlC2, Advanced Materials, 23, 4248 (2011). 2. B. Anasori, Y. Gogotsi (Ed.) 2D Metal Carbides and Nitrides (MXenes): Structure, Properties and Applications (Springer), 2019. 3. X. Wang, T. S. Mathis, K. Li, Z. Lin, L. Vlcek, T. Torita, N. C. Osti, C. Hatter, P. Urbankowski, A. Sarycheva, M. Tyagi, E. Mamontov, P. Simon, Y. Gogotsi, Solvents’ influence on charge storage in titanium carbide MXene, Nature Energy, 4, 241–248 (2019).