Department of Materials Science and Engineering, Stanford University, 496 Lomita Mall, Stanford, California 94305, USA.
Department of Electrical Engineering, Stanford University, 496 Lomita Mall, Stanford, California 94305, USA.
Nat Commun. 2017 Jan 16;8:14020. doi: 10.1038/ncomms14020.
Many energy storage materials undergo large volume changes during charging and discharging. The resulting stresses often lead to defect formation in the bulk, but less so in nanosized systems. Here, we capture in real time the mechanism of one such transformation-the hydrogenation of single-crystalline palladium nanocubes from 15 to 80 nm-to better understand the reason for this durability. First, using environmental scanning transmission electron microscopy, we monitor the hydrogen absorption process in real time with 3 nm resolution. Then, using dark-field imaging, we structurally examine the reaction intermediates with 1 nm resolution. The reaction proceeds through nucleation and growth of the new phase in corners of the nanocubes. As the hydrogenated phase propagates across the particles, portions of the lattice misorient by 1.5%, diminishing crystal quality. Once transformed, all the particles explored return to a pristine state. The nanoparticles' ability to remove crystallographic imperfections renders them more durable than their bulk counterparts.
许多储能材料在充电和放电过程中会经历大的体积变化。由此产生的应力通常会导致在大块材料中形成缺陷，但在纳米尺寸系统中则不那么常见。在这里，我们实时捕捉到了这样一种转变的机制——从 15 到 80nm 的单晶钯纳米立方体的加氢过程，以更好地理解这种耐久性的原因。首先，我们使用环境扫描透射电子显微镜以 3nm 的分辨率实时监测氢的吸收过程。然后，我们使用暗场成像以 1nm 的分辨率对反应中间体进行结构检查。反应通过纳米立方体角中新相的形核和生长进行。随着氢化相在颗粒中传播，晶格的部分错配度为 1.5%，降低了晶体质量。一旦转化，所有被探索的颗粒都恢复到原始状态。纳米颗粒去除晶体缺陷的能力使它们比其块状对应物更耐用。
