In Situ Detection of Active Edge Sites in Single-Layer MoS2 Catalysts

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• 作者：Albert Bruix ; Henrik G酶bel F眉chtbauer ; Anders K. Tuxen ; Alexander S. Walton ; Mie Andersen ; S酶ren Porsgaard ; Flemming Besenbacher ; Bj酶rk Hammer ; Jeppe V. Lauritsen
• 刊名：ACS Nano
• 出版年：2015
• 出版时间：September 22, 2015
• 年：2015
• 卷：9
• 期：9
• 页码：9322-9330
• 全文大小：600K
• ISSN：1936-086X

文摘

MoS₂ nanoparticles are proven catalysts for processes such as hydrodesulfurization and hydrogen evolution, but unravelling their atomic-scale structure under catalytic working conditions has remained significantly challenging. Ambient pressure X-ray Photoelectron Spectroscopy (AP-XPS) allows us to follow in situ the formation of the catalytically relevant MoS₂ edge sites in their active state. The XPS fingerprint is described by independent contributions to the Mo 3d core level spectrum whose relative intensity is sensitive to the thermodynamic conditions. Density Functional Theory (DFT) is used to model the triangular MoS₂ particles on Au(111) and identify the particular sulphidation state of the edge sites. A consistent picture emerges in which the core level shifts for the edge Mo atoms evolve counterintuitively toward higher binding energies when the active edges are reduced. The shift is explained by a surprising alteration in the metallic character of the edge sites, which is a distinct spectroscopic signature of the MoS₂ edges under working conditions.