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

Ryan Richards, Sarah Shulda, Louise Debefve, Adam Hoffman, Alexander Yeh, Ron Runnebaum, Ilke Arslan, Bruce Gates

Research output: Contribution to journalArticlepeer-review

10 Scopus Citations


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.

Original languageAmerican English
Pages (from-to)459-468
Number of pages10
JournalJournal of Physical Chemistry C
Issue number1
StatePublished - 9 Jan 2020

Bibliographical note

Publisher Copyright:
Copyright © 2019 American Chemical Society.

NREL Publication Number

  • NREL/JA-5100-75824


  • heavy metals
  • metal oxides
  • scanning transmission electron microscopy


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