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Mapping Catalytically Relevant Edge Electronic States of MoS2

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      Abstract

      Molybdenum disulfide (MoS 2) is a semiconducting transition metal dichalcogenide that is known to be a catalyst for both the hydrogen evolution reaction (HER) as well as for hydro-desulfurization (HDS) of sulfur-rich hydrocarbon fuels. Specifically, the edges of MoS 2 nanostructures are known to be far more catalytically active as compared to unmodified basal planes. However, in the absence of the precise details of the geometric and electronic structure of the active catalytic sites, a rational means of modulating edge reactivity remain to be developed. Here we demonstrate using first-principles calculations, X-ray absorption spectroscopy, as well as scanning transmission X-ray microscopy (STXM) imaging that edge corrugations yield distinctive spectroscopic signatures corresponding to increased localization of hybrid Mo 4d states. Independent spectroscopic signatures of such edge states are identified at both the S L 2,3 and S K-edges with distinctive spatial localization of such states observed in S L 2,3-edge STXM imaging. The presence of such low-energy hybrid states at the edge of the conduction band is seen to correlate with substantially enhanced electrocatalytic activity in terms of a lower Tafel slope and higher exchange current density. These results elucidate the nature of the edge electronic structure and provide a clear framework for its rational manipulation to enhance catalytic activity.

      Abstract

      Low-energy hybrid states at the bottom of the conduction band of MoS 2 thought to be involved in catalytic hydrogen evolution and hydro-desulfurization are spectrally distinguished and mapped, suggesting strong localization at the edges.

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            Author and article information

            Affiliations
            []Department of Chemistry and Department of Materials Science and Engineering, Texas A&M University , College Station, Texas 77845-3012, United States
            Molecular Foundry and §Advanced Light Source, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
            [# ]Department of Chemistry, Texas A&M University at Qatar , P.O. Box 23874, Doha, Qatar
            Author notes
            [* ](D.P.) E-mail: dgprendergast@ 123456lbl.gov .
            [* ](S.B.) E-mail: banerjee@ 123456chem.tamu.edu .
            Journal
            ACS Cent Sci
            ACS Cent Sci
            oc
            acscii
            ACS Central Science
            American Chemical Society
            2374-7943
            2374-7951
            03 April 2018
            25 April 2018
            : 4
            : 4
            : 493-503
            5920619 10.1021/acscentsci.8b00042
            Copyright © 2018 American Chemical Society

            This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes.

            Categories
            Research Article
            Custom metadata
            oc8b00042
            oc-2018-00042f

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