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Title: Iridium Atoms Bonded to Crystalline Powder MgO: Characterization by Imaging and Spectroscopy

Abstract

Samples with low loadings of metals on well-defined supports provide some of the best opportunities to determine the metal–support structure and bonding. We illustrate methods for characterizing atomically dispersed heavy metals on metal oxide supports by aberration-corrected scanning transmission electron microscopy (STEM) complemented by fluorescence detection extended X-ray absorption fine structure and infrared spectroscopies. STEM images of Ir atoms derived from Ir(C2H4)2(acac) (acac = acetylacetonato) on high-surface-area MgO powder were obtained with minimized electron beam damage by quickly recording images near where the focus had been established. The images show that iridium at a loading of 1.0 wt % on MgO calcined at 1073 K was atomically dispersed, populating much of the surface of the MgO particles, which had irregular shapes—consequently the Ir atoms were bonded at various sites to two or three surface O atoms. In contrast, MgO calcined at 1273 K consisted of almost perfectly cubic crystals, and Ir atoms at a loading of only 0.01 wt % on this nearly ideal support were anchored preferentially at edges and corners of the (100) faces and bonded to three surface O atoms. The latter results indicate a path forward for the determination of precise structures of atomically dispersed metalsmore » on crystalline metal oxide supports.« less

Authors:
ORCiD logo [1];  [2];  [3];  [3];  [4]; ORCiD logo [4];  [5]; ORCiD logo [3]
  1. Cornell Univ., Ithaca, NY (United States). Cornell High Energy Synchrotron Source (CHESS); Univ. of California, Davis, CA (United States)
  2. SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL); Univ. of California, Davis, CA (United States)
  3. Univ. of California, Davis, CA (United States)
  4. Colorado School of Mines, Golden, CO (United States). Dept. of Chemistry and Geochemistry; National Renewable Energy Lab. (NREL), Golden, CO (United States)
  5. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
OSTI Identifier:
1605337
Grant/Contract Number:  
AC02-76SF00515; FG02-04ER15513
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 124; Journal Issue: 1; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Imaging; Magnesium oxide; Metals; Scanning transmission electron microscopy; Transition metals

Citation Formats

Debefve, Louise M., Hoffman, Adam S., Yeh, Alexander J., Runnebaum, Ron C., Shulda, Sarah, Richards, Ryan M., Arslan, Ilke, and Gates, Bruce C.. Iridium Atoms Bonded to Crystalline Powder MgO: Characterization by Imaging and Spectroscopy. United States: N. p., 2019. Web. https://doi.org/10.1021/acs.jpcc.9b08592.
Debefve, Louise M., Hoffman, Adam S., Yeh, Alexander J., Runnebaum, Ron C., Shulda, Sarah, Richards, Ryan M., Arslan, Ilke, & Gates, Bruce C.. Iridium Atoms Bonded to Crystalline Powder MgO: Characterization by Imaging and Spectroscopy. United States. https://doi.org/10.1021/acs.jpcc.9b08592
Debefve, Louise M., Hoffman, Adam S., Yeh, Alexander J., Runnebaum, Ron C., Shulda, Sarah, Richards, Ryan M., Arslan, Ilke, and Gates, Bruce C.. Tue . "Iridium Atoms Bonded to Crystalline Powder MgO: Characterization by Imaging and Spectroscopy". United States. https://doi.org/10.1021/acs.jpcc.9b08592. https://www.osti.gov/servlets/purl/1605337.
@article{osti_1605337,
title = {Iridium Atoms Bonded to Crystalline Powder MgO: Characterization by Imaging and Spectroscopy},
author = {Debefve, Louise M. and Hoffman, Adam S. and Yeh, Alexander J. and Runnebaum, Ron C. and Shulda, Sarah and Richards, Ryan M. and Arslan, Ilke and Gates, Bruce C.},
abstractNote = {Samples with low loadings of metals on well-defined supports provide some of the best opportunities to determine the metal–support structure and bonding. We illustrate methods for characterizing atomically dispersed heavy metals on metal oxide supports by aberration-corrected scanning transmission electron microscopy (STEM) complemented by fluorescence detection extended X-ray absorption fine structure and infrared spectroscopies. STEM images of Ir atoms derived from Ir(C2H4)2(acac) (acac = acetylacetonato) on high-surface-area MgO powder were obtained with minimized electron beam damage by quickly recording images near where the focus had been established. The images show that iridium at a loading of 1.0 wt % on MgO calcined at 1073 K was atomically dispersed, populating much of the surface of the MgO particles, which had irregular shapes—consequently the Ir atoms were bonded at various sites to two or three surface O atoms. In contrast, MgO calcined at 1273 K consisted of almost perfectly cubic crystals, and Ir atoms at a loading of only 0.01 wt % on this nearly ideal support were anchored preferentially at edges and corners of the (100) faces and bonded to three surface O atoms. The latter results indicate a path forward for the determination of precise structures of atomically dispersed metals on crystalline metal oxide supports.},
doi = {10.1021/acs.jpcc.9b08592},
journal = {Journal of Physical Chemistry. C},
number = 1,
volume = 124,
place = {United States},
year = {2019},
month = {11}
}

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