Ding Li Ping, McLean Ben, Xu Ziwei, Kong Xiao, Hedman Daniel, Qiu Lu, Page Alister J, Ding Feng
Center for Multidimensional Carbon Materials (CMCM), Institute for Basic Science (IBS), Ulsan 44919, Republic of Korea.
Department of Optoelectronic Science & Technology, School of Electronic Information and Artificial Intelligence, Shanxi University of Science & Technology, Xi'an 710021, China.
J Am Chem Soc. 2022 Mar 30;144(12):5606-5613. doi: 10.1021/jacs.2c00879. Epub 2022 Mar 17.
Despite three decades of intense research efforts, the most fundamental question "why do carbon nanotubes grow?" remains unanswered. In fact, carbon nanotubes (CNTs) should not grow since the encapsulation of a catalyst with graphitic carbon is energetically more favorable than CNT growth in every aspect. Here, we answer this question using a theoretical model based on extensive first-principles and molecular dynamics calculations. We reveal a historically overlooked yet fundamental aspect of the CNT-catalyst interface, viz., that the interfacial energy of the CNT-catalyst edge is contact angle-dependent. The contact angle increases via graphitic cap lift-off, drastically decreasing the interfacial formation energy by up to 6-9 eV/nm, overcoming van der Waals cap-catalyst adhesion, and driving CNT growth. Mapping this remarkable and simple interplay allows us to understand, for the first time, why CNTs grow.
尽管经过三十年的深入研究，“碳纳米管为何生长？”这个最基本的问题仍然没有答案。事实上，碳纳米管（CNTs）本不应生长，因为用石墨碳包裹催化剂在各个方面在能量上都比碳纳米管生长更有利。在此，我们使用基于广泛的第一性原理和分子动力学计算的理论模型来回答这个问题。我们揭示了碳纳米管 - 催化剂界面一个历史上被忽视但却很基本的方面，即碳纳米管 - 催化剂边缘的界面能与接触角有关。接触角通过石墨帽的脱离而增大，极大地降低界面形成能达6 - 9电子伏特/纳米，克服范德华帽 - 催化剂附着力，并驱动碳纳米管生长。描绘这种显著而简单的相互作用使我们首次理解了碳纳米管为何生长。
