H. Karunadasa, E. Montalvo, Yujie Sun
Feb 10, 2012
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Science
Abstract
Edging In on MoS2 Molybdenum disulfide is a widely used catalyst in the petrochemical industry that has recently shown promise for water-splitting applications. Its activity appears to be confined to edge sites with exposed disulfide groups, although the precise geometric details underlying the chemistry remain uncertain. Karunadasa et al. (p. 698) prepared a molecular complex modeling one of these edge sites, in which a triangular Mo-S-S unit is supported by metal coordination to five tethered pyridine rings. The molecule was characterized crystallographically and proved robustly active toward electrochemical generation of hydrogen from water, even when applied to crudely filtered seawater. A small molecule functionally models the active component of an extended solid material with wide catalytic applications. Inorganic solids are an important class of catalysts that often derive their activity from sparse active sites that are structurally distinct from the inactive bulk. Rationally optimizing activity is therefore beholden to the challenges in studying these active sites in molecular detail. Here, we report a molecule that mimics the structure of the proposed triangular active edge site fragments of molybdenum disulfide (MoS2), a widely used industrial catalyst that has shown promise as a low-cost alternative to platinum for electrocatalytic hydrogen production. By leveraging the robust coordination environment of a pentapyridyl ligand, we synthesized and structurally characterized a well-defined MoIV-disulfide complex that, upon electrochemical reduction, can catalytically generate hydrogen from acidic organic media as well as from acidic water.