Fu Zhongheng; Wang Ning; Legut Dominik; Si Chen; Zhang Qianfan; Du Shiyu; Germann Timothy C.; Francisco Joseph S.; Zhang Ruifeng. Rational Design of Flexible Two-Dimensional MXenes with Multiple Functionalities. Chemical Reviews. 2019, vol. 119, issue 23, s. 11980-12031. ISSN 0009-2665, eISSN 1520-6890, DOI: https://doi.org/10.1021/acs.chemrev.9b00348.
The Review published in Chem. Rev., 119, 23, 11980–12031 (2019) is a comprehensive state-of-the-art study of the current status of knowledge of MXenes, a new class of 2D materials discovered within the last decade. MXenes are 2D materials derived from so-called MAX phases by etching Al layer. Therefore, it is not a single planar 2D material like graphene, silicene, hexagonal BN, etc., but layers of transitional metals (Tm) connected to either carbon, nitrogen or carbonitrides (Adv. Mater. 26, 7, 992-1005 (2014)). MXenes are very flexible and possible to functionalize their surfaces (by OH, F, O) and about 28 of them have been synthesized so far (Nat. Rev. Mater., 2, 2, 1-17 (2017)). The first part of the review deals with the thermodynamical, mechanical, and dynamical (atomic vibration) stability of 2D MXenes with respect to the various Tm, their combinations, functinalization, where for the first time we determined that oxygen at surface layer increase the ideal tensile and shear strengths by more than 30%. Otherwise, MXenes are very flexible (with strains up to 15%) and thus ideal candidates for, for example, electrode materials and displays that could be bended (Phys. Rev. B, 94, 10, 104103 (2016)). Indeed the second part of this review deals with the potential flexible applications of MXenes: (1) the fabrication of MXene-based flexible devices, such as electrical switches, micro elevators, and circuit breakers (Nano Energy, 17, 27-35 (2015)); (2) highly precise strain engineering at an atomic scale (Science, 354, 6315, 1031−1036 (2016)). This possibility to adsorb Li and other molecules results in possibility to use Mxenes for catalysis hydrogen(oxygen) evolution reaction for CO2 and nitrogen reduction as well as the energy storage materials (e.g. Li-anodes).