Kibsgaard Jakob, Lauritsen Jeppe V, Laegsgaard Erik, Clausen Bjerne S, Topsøe Henrik, Besenbacher Flemming
Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark.
J Am Chem Soc. 2006 Oct 25;128(42):13950-8. doi: 10.1021/ja0651106.
Supported MoS(2) nanoparticles constitute the active component of the important hydrotreating catalysts used for industrial upgrading and purification of the oil feedstock for the production of fossil fuels with a low environmental load. We have synthesized and studied a model system of the hydrotreating catalyst consisting of MoS(2) nanoclusters supported on a graphite surface in order to resolve a number of very fundamental questions related to the atomic-scale structure and morphology of the active clusters and in particular the effect of a substrate used in some types of hydrotreating catalysts. Scanning tunneling microscopy (STM) is used to image the atomic-scale structure of graphite-supported MoS(2) nanoclusters in real space. It is found that the pristine graphite (0001) surface does not support a high dispersion of MoS(2), but by introducing a small density of defects in the surface, highly dispersed MoS(2) nanoclusters could be synthesized on the graphite. From high-resolution STM images it is found that MoS(2) nanoclusters synthesized at low temperature in a sulfiding atmosphere preferentially grow as single-layer clusters, whereas clusters synthesized at 1200 K grow as multilayer slabs oriented with the MoS(2)(0001) basal plane parallel to the graphite surface. The morphology of both single-layer and multilayer MoS(2) nanoclusters is found to be preferentially hexagonal, and atom-resolved images of the top facet of the clusters provide new atomic-scale information on the MoS(2)-HOPG bonding. The structure of the two types of catalytically interesting edges terminating the hexagonal MoS(2) nanoclusters is also resolved in atomic detail in STM images, and from these images it is possible to reveal the atomic structure of both edges and the location and coverage of sulfur and hydrogen adsorbates.
负载型二硫化钼纳米颗粒是重要的加氢处理催化剂的活性成分，这些催化剂用于工业上对石油原料进行升级和提纯，以生产环境负荷低的化石燃料。我们合成并研究了一种加氢处理催化剂的模型体系，该体系由负载在石墨表面的二硫化钼纳米团簇组成，目的是解决一些与活性团簇的原子尺度结构和形态相关的非常基本的问题，特别是某些类型加氢处理催化剂中使用的底物的影响。扫描隧道显微镜（STM）用于在实空间中成像石墨负载的二硫化钼纳米团簇的原子尺度结构。发现原始石墨（0001）表面不能支持二硫化钼的高分散性，但通过在表面引入少量缺陷，可以在石墨上合成高度分散的二硫化钼纳米团簇。从高分辨率STM图像中发现，在硫化气氛中低温合成的二硫化钼纳米团簇优先生长为单层团簇，而在1200 K下合成的团簇则生长为多层板，其二硫化钼（0001）基面与石墨表面平行。发现单层和多层二硫化钼纳米团簇的形态优先为六边形，团簇顶面的原子分辨图像提供了关于二硫化钼与高定向热解石墨（HOPG）键合的新的原子尺度信息。在STM图像中也以原子细节解析了终止六边形二硫化钼纳米团簇的两种具有催化意义的边缘结构，从这些图像中可以揭示两种边缘的原子结构以及硫和氢吸附物的位置和覆盖情况。
