表面修饰对二维过渡金属碳、氮化物改性的理论研究

As a class family of two dimensional (2D) materials, two dimensional transition metal carbides or nitrides (MXenes) has been synthesized by recent experiments. Due to the metallic conductivity, MXenes have showing tremendous promise of applications in electrode materials, sensors, catalysis and electrochemical energy storage. Surface functional groups or defects are introduced on the surfaces inevitably in synthesis, which possess significant influences on their electronic structures and related properties, such as the regulation of band gaps or the introduction of magnetic properties. However, the effects of these surface functional groups or defects on the electronic structures of MXenes are not very clear. In addition, some results obtained from the first-principle calculations are inconsistent with the experiments. On the other hand, the adsorption of other types of atoms or molecules on their surface is expected to further regulate the electronic structures and modify the physical and chemical properties. Based on these issues, this research will investigate the modification of electronic structure and related properties of MXenes by adsorption of atoms or molecules. The results of this study will serve as a guidance for the synthesis of the high quality two-dimensional transition metal carbides or nitrides.

二维过渡金属碳、氮化物为近年来新合成的一类二维材料，一般具有金属导电性，在电极材料，传感器，催化和电化学能存储等领域具有巨大的应用前景。 表面官能团或者缺陷在这类材料的合成过程中被引入，对它们的电子结构及其相关性质产生重要影响，如打开带隙或引入磁性等。然而，这些表面官能团或缺陷对二维过渡金属碳、氮化物电子结构及其相关性质的影响还不是很清楚，一些理论预测结果也与实验存在较大出入。另一方面，在二维过渡金属碳、氮化物表面吸附其他类型的原子或分子基团有望进一步调控其电子结构并对其物理化学性质产生影响。现针对这些问题，本申请从表面修饰对二维过渡金属碳、氮化物电子结构的调控作用出发，研究表面吸附原子或小分子基团等对其电子结构及其相关性质的影响。本申请的研究结果将对实验上合成高质性能的二维过渡金属碳、氮材料具有重要的指导意义。

二维过渡金属碳、氮化物在电子器件，电催化，和电化学能存储等领域具有巨大的应用前景。申请人研究了表面官能团和缺陷对二维过渡金属碳、氮化物电子结构及其相关性质的影响。研究结果表明，选择MSSe单层不同表面（S或者Se）接触Hf2NT2(T=F, O, OH)可导致显著不同的肖特基势垒高(SHB)，甚至实现n型和p型的欧姆接触；Pt替位Mo2TiC2O2表面的O可以将H吸附的自由能调控到最佳值，使其电催化活性显著提高。SiS单层具有适中的带隙和平面内各向异性的载流子迁移性质，其在平面内x方向负泊松比值高达−0.19，为一种理想的拉胀材料；M-ScN和H-ScN单层均表现出很高的电子迁移率，具有在电子器件方面的应用价值，而O-ScN是一种有前景的二维拉胀和铁弹性材料。ZrC2单层的Na电化学容量高达932 mA h g-1，而Na在ZrC2单层的扩散势垒仅为0.02 eV，有望成为Na离子电池的电极材料；Ni掺杂g-GaN在析氧反应和氧还原反应的过电位分别为0.26和0.38 V，为高活性的双功能电催化剂。