二维TiC、Ti2C、Ti3C2表面吸附与电子结构特征的第一性原理研究

Recent experimental and theoretical researches show that Ti and C can form two dimension TiC, Ti2C, and Ti3C2 structures. Owing to the high specific surface area and special electronic structures, these two dimension materials has the important academic value and the application value in many areas, such as lithium ion battery, electronic transport, adsorption. Surface adsorption is among the key processes of the storage and application of TiC, Ti2C, and Ti3C2 structures. Researches of it also help to further investigate the features of the electronic structures. In this program, by using the first principles density functional theory, we will simulate the adsorption of O2、H2、N2、CO、H2O、NH3 on two dimension TiC、Ti2C、Ti3C2 surface, analyze the surface adsorption activities, the selectivity of adsorption, the influence of coverage on adsorption. We will study the relevant changes of the electronic structures caused by the adsorption in particular. Though these studies, we will further investigate the characters of the electronic structures and the influence of adsorption on electronic structures and relevant electromagnetic properties completely. This program makes preparation for the study of the stability of two dimension structures, and provides theoretic assistance for the application studies of TiC, Ti2C, and Ti3C2 structures.

最近的实验与理论研究发现Ti、C元素可以形成二维TiC、Ti2C、Ti3C2结构。由于高的比表面积与特殊的电子结构，这类新材料在锂离子电池、电子输运、吸附等领域具有重要的学术研究与应用价值。表面吸附是该类材料在储存与应用过程中所涉及的一类关键过程。同时，表面吸附研究也有助于我们深入探究材料的电子结构特征。本项目采用第一性原理的密度泛函理论方法，对二维TiC、Ti2C、Ti3C2表面的O2、H2、N2、CO、H2O、NH3等气体吸附进行模拟，分析二维TiC、Ti2C、Ti3C2表面吸附活性、吸附选择性，以及覆盖度对吸附的影响，并着重研究吸附引起的电子结构变化。通过这些研究，我们将深入探究二维TiC、Ti2C、Ti3C2的表面电子结构特征以及吸附对电子结构和相关电磁学性质的影响。该项目为二维材料的稳定性研究创造基础，也为这类材料的应用研究提供理论支持。

应用密度泛函理论，TiC、Ti2C、Ti3C2表面吸附活性与电子结构特征得到了研究。计算结果显示二维TiC表面Ti原子对H2的化学吸附为Kubas吸附，由Ti-3d轨道与C-2p轨道耦合引起。Ti2C、Ti3C2表面未极化的Ti-3d轨道使得它们极易与O2、H2O反应，形成Tin+1CnO2-2xOH2x结构。Tin+1CnO2-2xOH2x表面O原子的电子轨道填充度较高，对Au原子的吸附活性较弱。表面OH基团对Au原子的吸附活性随x的增大而增强。最后，我们研究了MXene的前驱体-Mn+1ACn结构，发现MC为缺电子体系，趋向于与MA形成Mn+1ACn结构。并且n=1时的M2AC的形成焓最大，较容易被制备出来。M2AlC 和M2SiC 较为容易地被分离成二维M2C 结构。