Bruix Albert, Lauritsen Jeppe V, Hammer Bjørk
Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark.
Nanoscale. 2021 Jun 14;13(22):10167-10180. doi: 10.1039/d0nr08598g. Epub 2021 Jun 1.
Nanomaterials based on MoS and related transition metal dichalcogenides (TMDCs) are remarkably versatile; MoS nanoparticles are proven catalysts for processes such as hydrodesulphurization and the hydrogen evolution reaction, and transition metal dichalcogenides in general have recently emerged as novel 2D components for nanoscale electronics and optoelectronics. The properties of such materials are intimately related to their structure and dimensionality. For example, only the edges exposed by MoS nanoparticles (NPs) are catalytically active, and extended MoS systems show different character (direct or indirect gap semiconducting, or metallic) depending on their thickness and crystallographic phase. In this work, we show how particle size and interaction with a metal surface affect the stability and properties of different MoS NPs and the resulting phase diagrams. By means of calculations based on the Density Functional Theory (DFT), we address how support interactions affect MoS nanoparticles of varying size, composition, and structure. We demonstrate that interaction with Au modifies the relative stability of the different nanoparticle types so that edge terminations and crystallographic phases that are metastable for free-standing nanoparticles and monolayers are expressed in the supported system. These support-effects are strongly size-dependent due to the mismatch between Au and MoS lattices, which explains experimentally observed transitions in the structural phases for supported MoS NPs. Accounting for vdW interactions and the contraction of the Au(111) surface underneath the MoS is further found to be necessary for quantitatively reproducing experimental results. We finally find that support-induced effects on the stability of nanoparticle structures are general to TMDC nanoparticles on metal surfaces, which we demonstrate also for MoS on Au(111), WS on Au(111), and WS on Ag(111). This work demonstrates how the properties of nanostructured transition metal dichalcogenides and similar layered systems can be modified by the choice of supporting metal.
基于MoS及相关过渡金属二硫属化物（TMDCs）的纳米材料具有显著的多功能性；MoS纳米颗粒已被证明是加氢脱硫和析氢反应等过程的催化剂，而一般来说，过渡金属二硫属化物最近已成为纳米级电子学和光电子学的新型二维组件。这类材料的性质与其结构和维度密切相关。例如，只有MoS纳米颗粒（NPs）暴露的边缘具有催化活性，而扩展的MoS体系根据其厚度和晶体相表现出不同的特性（直接或间接带隙半导体，或金属性）。在这项工作中，我们展示了粒径以及与金属表面的相互作用如何影响不同MoS NPs的稳定性和性质以及由此产生的相图。通过基于密度泛函理论（DFT）的计算，我们研究了载体相互作用如何影响不同尺寸、组成和结构的MoS纳米颗粒。我们证明，与Au的相互作用改变了不同类型纳米颗粒的相对稳定性，使得对于独立的纳米颗粒和单分子层来说亚稳的边缘终止和晶体相在负载体系中得以体现。由于Au和MoS晶格之间的失配，这些载体效应强烈依赖于尺寸，这解释了实验观察到的负载型MoS NPs结构相的转变。进一步发现，考虑范德华相互作用以及MoS下方Au(111)表面的收缩对于定量重现实验结果是必要的。我们最终发现，载体对纳米颗粒结构稳定性的诱导效应对于金属表面的TMDC纳米颗粒是普遍存在的，我们还对Au(111)上的MoS、Au(111)上的WS以及Ag(111)上的WS进行了验证。这项工作展示了如何通过选择支撑金属来改变纳米结构的过渡金属二硫属化物和类似层状体系的性质。
