制备条件对MXene形貌、结构与电化学性能的影响

Effects of Preparation Conditions on the Morphologies,Structures and Electrochemical Properties of MXene

以Ti3AlC2为原料,采用LiF+HCl一步刻蚀-插层制备Ti3C2Tx,进一步通过超声处理得到单层或少层的MXene.利用X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和电化学测试对样品的结构、形貌和电化学性能进行了研究.通过改变刻蚀剂的比例及超声剥离时间,研究了不同刻蚀条件和剥离条件对二维晶体Ti3C2Tx的形貌、结构和电化学性能的影响.结果表明,制备条件对MXene的片层结构和性能具有较大的影响.当HCl浓度为6mol/L,LiF与Ti3AlC2的摩尔比为7.5,超声时间为1h时,所得MXene具有较小的晶格常数和较大的片层尺寸,片层尺寸可达1μm,具有较多的表面含氧官能团,电化学性能最佳,在0.5A/g的电流密度下,质量比容量达到342F/g,当电流密度提高至20A/g时,质量比容量仍可保持244F/g,在1A/g电流密度下循环10000周后,容量仍能保留87%左右,表现出较好的倍率性能与循环稳定性.

Using Ti3AlC2 as precursor, multilayered Ti3C2Tx were prepared and intercalated in one process with LiF+HCl as etchant, and then single or few layers of two-dimensional(2D) MXene flakes were delaminated with following sonication. The studies were focused on the effects of etching and delamination conditions by tuning the ratios of etchant/Ti3AlC2(molar ratio) and the sonication time on the morphologies, structures and electrochemical properties of two dimensional crystal flakes of Ti3C2Tx. The results showed that selecting appropriate fabrication conditions is crucial to the structures and properties of MXene flakes. It is shown that the MXene obtained with 6 mol/L HCl, the LiF/Ti3AlC2 molar ratio of 7.5 and the sonication time of 1 h which named FMX7.5-6′ displayed a small lattice constant and a large flake size up to 1 μm. It also had a high content of oxygen-containing functional groups and demonstrated the best electrochemical properties. At the current density of 0.5 A/g, it demonstrated a high specific capacity of 342F/g and its capacity could reach 244 F/g at the current density of 20 A/g. The specific capacity could remain 87% of the original value after 10000 cycling test at the current density of 1 A/g, showing a good rate and stability performance.