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二维（2D）过渡金属双硫属化合物（TMDC）已显示出优异的电子、磁性、光学、力学和催化性能。由2D TMDC的一维（1D）边缘所代表的不连续性，类似块体材料的表面，它可以赋予材料新特性、新功能。如，2D MoS2单层是带隙为1.8 eV的直接间隙半导体，而1D MoS2的锯齿形（ZZ）边缘是金属的。此外，正是2D TMDC的边缘才具有高催化活性，而基础平面却表现为化学惰性。因此，了解2D TMDC中边缘的特性以及合成条件，对于设计新功能材料来说至关重要。
由于2D过渡金属二硫化碳（TMDC）中整个可合成的重构边缘家族仍然未知，该研究开发出了一种计算方法，可以快速有效地发现2D TMDC系列中更多可合成的功能性边缘，为计算筛选和发现其他功能重构的TMDC边缘提供了独特的机会。在本研究中，我们提出了这样一种计算方法。来自美国橡树岭国家实验室纳米材料科学中心的胡国祥和P. Ganesh共同领导的研究团队，从构象集成-生成开始，使用计算上可承受的力场方法，筛选了稳定边缘。然后，使用基于DFT的电子结构计算，进一步完善了所获得的稳定边缘，以生成相位图并筛选其功能特性。以MoS2为例，我们筛选了625种2H和1T MoS2相的边缘构象，并预测了稳定的边缘以指导实验合成。随后，他们研究了这些边缘的功能特性，并发现许多这些内在可调的边缘重构，对于HER来说是最佳的。因此，他们的研究为预测2D材料的可合成的功能边缘，提供了一种全面而负担得起的计算方案，并为实验研究人员提供了有用的指导。许多研究已经探索了通过Edisonian方法中的外部掺杂来调节TMDC的催化、电子和磁性能，但该研究的优点是发现了一系列“本征”（基于金属/硫属元素比）可调材料，而且各种功能特性可调范围广泛。他们的成功探索，开启了一种新的由设计而发现新材料的范式，可搜索和发现其他具有特定多功能的、有潜在边缘多型性的2D“本征”边缘重构系列，并适用于广泛的纳米级应用。该文近期发表于npj Computational Materials 6: 44 (2020)，英文标题与摘要如下，点击左下角“阅读原文”可以自由获取论文PDF。
Predicting synthesizable multi-functional edge reconstructions in two-dimensional transition metal dichalcogenides
Guoxiang Hu, Victor Fung, Xiahan Sang, Raymond R. Unocic & P. Ganesh
Two-dimensional (2D) transition metal dichalcogenides (TMDCs) have attracted tremendous interest as functional materials due to their exceptionally diverse and tunable properties, especially in their edges. In addition to the conventional armchair and zigzag edges common to hexagonal 2D materials, more complex edge reconstructions can be realized through careful control over the synthesis conditions. However, the whole family of synthesizable, reconstructed edges remains poorly studied. Here, we develop a computational approach integrating ensemble-generation, force-relaxation, and electronic-structure calculations to systematically and efficiently discover additional reconstructed edges and screen their functional properties. Using MoS2 as a model system, we screened hundreds of edge-reconstruction to discover over 160 reconstructed edges to be more stable than the conventional ones. More excitingly, we discovered nine new synthesizable reconstructred edges with record thermodynamic stability, in addition to successfully reproducing three recently synthesized edges. We also find our predicted reconstructed edges to have multi-functional properties—they show near optimal hydrogen evolution activity over the conventional edges, ideal for catalyzing hydrogen-evolution reaction (HER) and also exhibit half-metallicity with a broad variation in magnetic moments, making them uniquely suitable for nanospintronic applications. Our work reveals the existence of a wide family of synthesizable, reconstructed edges in 2D TMDCs and opens a new materials-by-design paradigm of ‘intrinsic’ edge engineering multifunctionality in 2D materials.
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