Department of Materials Science and NanoEngineering , Rice University , Houston , Texas 77005 , United States.
Nano Lett. 2018 Aug 8;18(8):5288-5293. doi: 10.1021/acs.nanolett.8b02283. Epub 2018 Jul 10.
Solid Co-W catalysts have been shown to yield single-walled carbon nanotubes (CNT) with high selectivity, simplistically attributed to CNT-catalyst symmetry match for certain chiral indices ( n, m). Here, based on large-scale first-principles calculations combined with kinetic Monte Carlo simulations, we show instead that such selectivity arises from a complex kinetics of growth. The solid CoW catalyst strongly favors a restructured, asymmetric CNT edge which entails preferential nucleation of tubes with 2 m < n but much faster growth of chiral tubes with n ⩽ 2 m. We uncover a tendency of interface defects formation that, although rare, drive CNT type change from smaller to larger chiral angles (zigzag to armchair). Being both least prone to defects and fast growing, the (12,6) CNT appears as a transient, kinetics-selected type reaching highest abundance.
固溶 Co-W 催化剂已被证明可高效选择性地合成单壁碳纳米管（CNT），这一现象通常归因于 CNT-催化剂的手性指数（n，m）对称性匹配。在此，我们基于大规模第一性原理计算和动力学蒙特卡罗模拟发现，这种选择性源于复杂的生长动力学。固溶 Co-W 催化剂强烈倾向于形成重构的、不对称的 CNT 边缘，这需要优先成核具有 2m<n 的管，但 n ⩽ 2m 的手性管具有更快的生长速度。我们揭示了界面缺陷形成的趋势，尽管这种趋势很少见，但它促使 CNT 类型从较小的手性角（锯齿型）转变为较大的手性角（扶手椅型）。（12,6）CNT 不仅最不易形成缺陷，而且生长速度也最快，因此作为一种瞬态、动力学选择的类型达到了最高丰度。
