Migration of Single Iridium Atoms and Tri-iridium Clusters on MgO Surfaces: Aberration-Corrected STEM Imaging and Ab Initio Calculations

Chang Wan Han; Hakim Iddir; Alper Uzun; Larry A Curtiss; Nigel D Browning; Bruce C Gates; Volkan Ortalan

doi:10.1021/acs.jpclett.5b01884

Migration of Single Iridium Atoms and Tri-iridium Clusters on MgO Surfaces: Aberration-Corrected STEM Imaging and Ab Initio Calculations

J Phys Chem Lett. 2015 Dec 3;6(23):4675-9. doi: 10.1021/acs.jpclett.5b01884. Epub 2015 Nov 12.

Authors

Chang Wan Han^{1

2}, Hakim Iddir³, Alper Uzun⁴, Larry A Curtiss³, Nigel D Browning⁵, Bruce C Gates⁶, Volkan Ortalan^{1

2}

Affiliations

¹ School of Materials Engineering, Purdue University , West Lafayette, Indiana 47907, United States.
² Birck Nanotechnology Center, Purdue University , West Lafayette, Indiana 47907, United States.
³ Materials Science Division, Argonne National Laboratory , Lemont, Illinois 60439, United States.
⁴ Department of Chemical and Biological Engineering, Koç University , Sariyer, Istanbul 34459, Turkey.
⁵ Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory , P.O. Box 999, Richland, Washington 99352, United States.
⁶ Department of Chemical Engineering & Materials Science, University of California , Davis, California 95616, United States.

PMID: 26544015
DOI: 10.1021/acs.jpclett.5b01884

Abstract

To address the challenge of fast, direct atomic-scale visualization of the migration of atoms and clusters on surfaces, we used aberration-corrected scanning transmission electron microscopy (STEM) with high scan speeds (as little as ∼0.1 s per frame) to visualize the migration of (1) a heavy atom (Ir) on the surface of a support consisting of light atoms, MgO(100), and (2) an Ir3 cluster on MgO(110). Sequential Z-contrast images elucidate the surface transport mechanisms. Density functional theory (DFT) calculations provided estimates of the migration energy barriers and binding energies of the iridium species to the surfaces. The results show how the combination of fast-scan STEM and DFT calculations allow visualization and fundamental understanding of surface migration phenomena pertaining to supported catalysts and other materials.

Keywords: density functional theory; heterogeneous catalysis; scanning transmission electron microscopy; supported catalysts; surface diffusion.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.