Element Replacement Approach by Reaction with Lewis Acidic Molten Salts to Synthesize Nanolaminated MAX Phases and MXenes
Element Replacement Approach by Reaction with Lewis Acidic Molten Salts to Synthesize Nanolaminated MAX Phases and MXenes
复制标题
通过与路易斯酸性熔盐反应合成纳米层压 MAX 相和 MXene 的元素替换方法
DOI：
10.1021/jacs.9b00574
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发表时间：
2019-03-20
影响因子：
15
通讯作者：
Huang, Qing
中科院分区：
文献类型：
--
作者：
Li, Mian;Lu, Jun;Huang, Qing
纳米层压材料因其优异的性能和广泛的应用而非常重要。在这里，我们展示了一个通用的方法来合成一系列的锌基MAX相和Cl-终止MXene起源于MAX相和后过渡金属卤化物之间的置换反应。该方法是自上而下的路线，其使得后过渡元素原子（在本情况下为Zn）能够占据预先存在的MAX相结构中的A位点。利用来自熔融ZnCl 2的Zn元素与MAX相前体（Ti 3AlC 2、Ti 2AlC、Ti 2AlN和V2 AlC）中的Al元素之间的这种置换反应，合成了新型MAX相Ti 3 ZnC 2、Ti 2 ZnC、Ti 2 ZnN和V2 ZnC。当使用过量的ZnCl 2时，由于熔融ZnCl 2的强刘易斯酸性，通过随后的Ti 3 ZnC 2和Ti 2 ZnC的剥落得到Cl封端的MXene（例如Ti 3 C2 Cl 2和Ti 2 CCl 2）。这些结果表明，A位元素在传统的MAX相的后过渡金属卤化物的替代打开了大门，探索MAX相，在高温下是不稳定的，将难以通过常用的粉末冶金方法合成。此外，这是第一次获得完全Cl-封端的MXene，并且刘易斯酸在熔融盐中的蚀刻效应提供了通过无HF化学方法制备MXene的绿色和可行的路线。
Nanolaminated materials are important because of their exceptional properties and wide range of applications. Here, we demonstrate a general approach to synthesizing a series of Zn-based MAX phases and Cl-terminated MXenes originating from the replacement reaction between the MAX phase and the late transition-metal halides. The approach is a top-down route that enables the late transitional element atom (Zn in the present case) to occupy the A site in the pre-existing MAX phase structure. Using this replacement reaction between the Zn element from molten ZnCl2 and the Al element in MAX phase precursors (Ti3AlC2, Ti2AlC, Ti2AlN, and V2AlC), novel MAX phases Ti3ZnC2, Ti2ZnC, Ti2ZnN, and V2ZnC were synthesized. When employing excess ZnCl2, Cl-terminated MXenes (such as Ti3C2Cl2 and Ti2CCl2) were derived by a subsequent exfoliation of Ti3ZnC2 and Ti2ZnC due to the strong Lewis acidity of molten ZnCl2. These results indicate that A-site element replacement in traditional MAX phases by late transition-metal halides opens the door to explore MAX phases that are not thermodynamically stable at high temperature and would be difficult to synthesize through the commonly employed powder metallurgy approach. In addition, this is the first time that exclusively Cl-terminated MXenes were obtained, and the etching effect of Lewis acid in molten salts provides a green and viable route to preparing MXenes through an HF-free chemical approach.