低电压STEM-EELS在纳米催化剂结构表征中的应用
许名权#，李傲雯#，周 武*
（中国科学院大学 物理科学学院，北京100049）
摘 要 低电压球差校正扫描透射电子显微学和电子能量损失谱(STEM-EELS)由于能够有效地避免撞击位移损伤(knock-on damage)和提高电子束与样品的非弹性散射截面，从而在低维纳米催化剂的结构表征方面具有广阔的应用前景。作者以最近在CrNi氧化物和Ni-N-C单原子催化剂上的工作为例，展示利用低电压STEM-EELS表征不同元素不同化合价态在空间上的分布以及在单原子敏感度下进行化学键合的分析。这些基于低加速电压下的STEM-EELS结果为理解纳米催化剂的构效关系提供了更全面的认识以及为材料设计提供了进一步指导。
关键词 单原子；低电压；扫描透射电子显微学；电子能量损失谱；纳米催化剂
中图分类号：TG115.21+5.3
文献标识码：Adoi:10.3969/j.issn.1000-6281.2020.05.012
Low-voltage STEM-EELS for the structural characterization of nano-catalysts
XU Ming-quan#, LI Ao-wen#, ZHOU Wu*
（School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China）
Abstract Electron energy loss spectroscopy (EELS) coupled with aberration corrected scanning transmission electron microscopy (STEM) at low accelerating voltage has promising applications on the structural characterization of low-dimensional nano-catalysts. By reducing the energy of the electron, the knock-on damage to the sample can be minimized while the inelastic scattering cross-section is increased for a better signal-to-noise ratio in EELS. Here, we use our recent works on CrNi mixed oxides and Ni-N-C single atom catalysts as examples to demonstrate the spatial mapping of valence states of different elements and analyze the chemical bonding with single-atom sensitivity using low-voltage STEM-EELS. The STEM-EELS results provide a more comprehensive view for the structure-property relationships of these nano-catalysts and offer valuable guidance for material design.
Keywords single atom; low-voltage; scanning transmission electron microscopy; electron energy loss spectroscopy; nano-catalysts
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