Chemical Origin of Termination-Functionalized MXenes: Ti3C2T2 as a Case Study

作者：Tao Hu, Zhaojin Li, Minmin Hu, Jiemin Wang, Qing‐Miao Hu, Qingzhong Li, Xiaohui Wang · 发表于：The Journal of Physical Chemistry C · 年份：2017 · DOI：10.1021/acs.jpcc.7b05675 · 被引用次数：299 · 研究领域：MXene and MAX Phase Materials、2D Materials and Applications、Ferroelectric and Negative Capacitance Devices

MXenes represent a burgeoning family of two-dimensional (2D) functional materials with a variety of applications that highly rely on termination-mediated surface functionalization, but the understanding of termination is limited. Here, we take Ti 3 C 2 T 2 ( T = O, F, OH, and H) as an example of MXenes, to demonstrate how termination stabilizes the Ti 3 C 2 monolayer matrix by saturating the nonbonding valence electrons of the surface Ti atom by the low-energy orbitals of the termination. This is achieved by orbitally resolved density of states analysis by simply yet efficiently manipulating the internal coordination of the octahedral crystal field to match exactly the Cartesian coordination. Highly degenerate 3d orbitals of surface Ti split in such a way that it exhibits pseudogaps whose widths predict a stability order Ti 3 C 2 O 2 > Ti 3 C 2 F 2 > Ti 3 C 2 (OH) 2 > Ti 3 C 2 H 2 > Ti 3 C 2, consistent with Bader charge analysis, thermodynamic calculations, and experimental results. This new criterion could have implications in the general context of ubiquitous termination phenomena of MXenes and other relevant termination-functionalized 2D materials.