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

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• 作者：Chang Wan Han ; Hakim Iddir ; Alper Uzun ; Larry A. Curtiss ; Nigel D. Browning ; Bruce C. Gates ; Volkan Ortalan
• 刊名：The Journal of Physical Chemistry Letters
• 出版年：2015
• 出版时间：December 3, 2015
• 年：2015
• 卷：6
• 期：23
• 页码：4675-4679
• 全文大小：376K
• ISSN：1948-7185

文摘

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 鈭?.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.