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首页> 外文期刊>Catalysis science & technology >HRTEM and molecular modeling of the MoS2-Co9S8 interface: understanding the promotion effect in bulk HDS catalysts
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HRTEM and molecular modeling of the MoS2-Co9S8 interface: understanding the promotion effect in bulk HDS catalysts

机译：MOS2-CO9S8界面的HRTEM和分子建模：了解大量HDS催化剂的促进效应

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As environmental regulations increase, more selective transition metal sulfide (TMS) catalytic materials for hydrotreating applications are needed. Highly active TMS catalysts become more and more desirable triggering new interest for unsupported Co-promoted MoS2-based systems that have high volumetric activity as reported here. Contrary to the common observation for alumina-supported MoS2-based catalysts, we found in our previous studies with dibenzothiophene (DBT) hydrodesulfurization (HDS) that the catalytic activity is directly proportional to the increase of surface area of the sulfide phases (Co9S8 and MoS2) present in Co-promoted MoS2 unsupported catalysts. This suggests that activity is directly connected with an increase of the contact surface area between the two sulfide phases. Understanding of the nature of the possible interaction between MoS2 and Co9S8 in unsupported catalytic systems is therefore critical in order to get a more generalized overview of the causes for synergy. This has been achieved herein through the detailed characterization by XRD, XPS, and HRTEM of the highly active Co9S8/ MoS2 catalyst resulting in a proposed model for a Co9S8/MoS2 interface. This model was then subjected to a DFT analysis to determine a reasonable description of the surface contact region between the two bulk phases. Modelling of the interface shows the creation of open latent vacancy sites on Mo atoms interacting with Co and formation of direct Co-Mo bonds. Strong electron donation from Co to Mo also occurs through the intermediate sulfur atom bonded to both metals while an enhanced metallic character is also found. These changes in coordination and electronic properties are expected to favor a synergetic effect between Co and Mo at the proposed localized interface region between the two bulk MoS2 and Co9S8 phases.
机译：随着环境法规的增加，需要更具选择性的过渡金属硫化物（TMS）催化材料，用于水力处理应用。高度活跃的TMS催化剂变得越来越需要，引发了无支撑的基于MOS2的无支撑的基于MOS2的系统，这些系统具有高体积活性，如此处报道。与对氧化铝基于MOS2的催化剂的共同观察相反，我们在先前对Dibenzothiophene（DBT）氢化硫化（HDS）的研究中发现，该催化活性与硫化物相（CO9S8和MOS2和MOS2的表面积增加）成正比）存在于联合促进的MOS2中，无支撑的催化剂。这表明活动与两个硫化物相之间的接触表面积的增加直接相关。因此，了解不支持的催化系统中MOS2与CO9S8之间可能相互作用的性质至关重要，对于为了获得协同作用的原因而言，至关重要。本文通过高度活性CO9S8/ MOS2催化剂的XRD，XP和HRTEM的详细表征实现了这一点，从而为CO9S8/ MOS2界面提供了建议的模型。然后对该模型进行DFT分析，以确定对两个散装相之间表面接触区域的合理描述。界面的建模显示在与CO相互作用的MO原子上创建开放的潜空位点并形成直接的Co-MO键。从CO到MO的强额捐赠也通过与两种金属键合的中间硫原子进行，同时还发现了增强的金属特性。预计在两个散装MOS2和CO9S8阶段之间所提出的局部界面区域的CO和MO之间的协调和电子特性变化有利于CO和MO之间的协同作用。

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