Why Carbon Nanotubes Grow.

Li Ping Ding, Ben McLean, Ziwei Xu, Xiao Kong, Daniel Hedman, Lu Qiu, Alister J Page, Feng Ding

Journal of the American Chemical Society 2022 Mar 30

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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.

Citation

Li Ping Ding, Ben McLean, Ziwei Xu, Xiao Kong, Daniel Hedman, Lu Qiu, Alister J Page, Feng Ding. Why Carbon Nanotubes Grow. Journal of the American Chemical Society. 2022 Mar 30;144(12):5606-5613