Obtaining Ambient‐Stable MXene Ti<sub>3</sub>C<sub>2</sub>T<i><sub>x</sub></i> through Avoidance of Surface Oxidation Active Sites
Xuesong Li, Xue Ni, Qian Yao, Liuyuan Han, Xiangyan Zhao, Bo Li, Tao He, Xutang Tao
Abstract
Abstract As the quintessential representation of MXenes, Ti 3 C 2 T x has attracted widespread scientific interest and has demonstrated unparalleled potential in various applications. However, Ti 3 C 2 T x has always been subject to its ambient instability, which deteriorates the intrinsic properties and limits the practical applications. The mechanism responsible for oxidative degradation of Ti 3 C 2 T x has remained elusive, and the subsequent improvement of the preparation for ambient‐stable Ti 3 C 2 T x is still a challenge. In this paper, the ambient instability of Ti 3 C 2 T x is found to be attributed to the presence of many oxidation active sites on the surface, the formation of which is highly correlated with the enrichment of etching by‐products (AlF x or Al(OF) x ). Based on the above findings a slow‐speed etching method is designed, using tetramethylammonium hydroxide as a separate etching‐agent, to avoid adsorption of fluorine‐containing by‐products during etching. The prepared high‐quality Ti 3 C 2 T x flakes exhibit excellent ambient stability even after 4 months of dispersion in water, unlike conventional aqueous Ti 3 C 2 T x dispersions that can only be kept for a few days. The intrinsic stability allows Ti 3 C 2 T x to avoid its decomposition in seawater desalination, and it exhibits superior desalination ability with a maximum reduction of 62.2% in Na + permeability and a maximum increase of 300% in water flux.