Atomic-scale structural identification and evolution of Co-W-C ternary SWCNT catalytic nanoparticles: High-resolution STEM imaging on SiO<sub>2</sub>.

An, Hua; Kumamoto, Akihito; Xiang, Rong; Inoue, Taiki; Otsuka, Keigo; Chiashi, Shohei; Bichara, Christophe; Loiseau, Annick et al. · Sci Adv · 2019

basic_science · Level V

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Abstract

Recently, W-based catalysts have provided a promising route to synthesize single-walled carbon nanotubes (SWCNTs) with specific chirality, but the mechanism of the growth selectivity is vaguely understood. We propose a strategy to identify the atomic structure as well as the structure evolution of the Co-W-C ternary SWCNT catalyst. The key is to use a thin SiO<sub>2</sub> film as the catalyst support and observation window. As the catalyst is uniformly prepared on this SiO<sub>2</sub> film and directly used for the SWCNT synthesis, this method has an advantage over conventional methods: it creates an opportunity to obtain original, statistical, and dynamic understanding of the catalyst. As a technique, atomic-scale imaging directly on SiO<sub>2</sub> serves as a powerful and versatile tool to investigate nanocrystals and high-temperature reactions; for the synthesis of SWCNTs, this work successfully visualizes the structure and evolution of the catalyst and illuminates the possible nucleation sites of the chirality-specific growth.