3 years ago

High-Energy-Resolution X-ray Absorption Spectroscopy for Identification of Reactive Surface Species on Supported Single-Site Iridium Catalysts

High-Energy-Resolution X-ray Absorption Spectroscopy for Identification of Reactive Surface Species on Supported Single-Site Iridium Catalysts
Louise M. Debefve, David A. Dixon, Simon R. Bare, Shengjie Zhang, Bruce C. Gates, Alessandro Gallo, Chia-Yu Fang, Dimosthenis Sokaras, Thomas Kroll, Adam S. Hoffman
We report high-energy-resolution X-ray absorption spectroscopy detection of ethylene and CO ligands adsorbed on catalytically active iridium centers isolated on zeolite HY and on MgO supports. The data are supported by density functional theory and FEFF X-ray absorption near-edge modelling, together with infrared (IR) spectra. The results demonstrate that high-energy-resolution X-ray absorption spectra near the iridium LIII (2p3/2) edge provide clearly ascribable, distinctive signatures of the ethylene and CO ligands and illustrate effects of supports and other ligands. This X-ray absorption technique is markedly more sensitive than conventional IR spectroscopy for characterizing surface intermediates, and it is applicable to samples having low metal loadings and in reactive atmospheres and is expected to have an increasing role in catalysis research by facilitating the determination of mechanisms of solid-catalyzed reactions through identification of reaction intermediates in working catalysts. Beam me up, Scotty! High-energy-resolution X-ray absorption spectroscopy is combined with density functional theory and FEFF simulations ascribing spectral features to adsorbates on single-site supported iridium catalyst, pushing detection limits below those of conventional infrared spectroscopy.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/chem.201701459

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