Han Chang Wan, Iddir Hakim, Uzun Alper, Curtiss Larry A, Browning Nigel D, Gates Bruce C, Ortalan Volkan
School of Materials Engineering, Purdue University , West Lafayette, Indiana 47907, United States.
Birck Nanotechnology Center, Purdue University , West Lafayette, Indiana 47907, United States.
J Phys Chem Lett. 2015 Dec 3;6(23):4675-9. doi: 10.1021/acs.jpclett.5b01884. Epub 2015 Nov 12.
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.
为应对在表面上对原子和原子团迁移进行快速、直接的原子尺度可视化这一挑战，我们使用了具有高扫描速度（低至每帧约0.1秒）的像差校正扫描透射电子显微镜（STEM），以可视化（1）重原子（Ir）在由轻原子组成的载体MgO(100)表面上的迁移，以及（2）Ir3团簇在MgO(110)上的迁移。连续的Z衬度图像阐明了表面传输机制。密度泛函理论（DFT）计算提供了铱物种在表面上的迁移能垒和结合能的估计值。结果表明，快速扫描STEM和DFT计算的结合如何能够实现对与负载型催化剂及其他材料相关的表面迁移现象的可视化和基本理解。
