Atomic self‐reconstruction of catalyst dominated growth mechanism of graphite structures
Atomic self‐reconstruction of catalyst dominated growth mechanism of graphite structures
复制标题
原子自重构催化剂主导的石墨结构生长机制
DOI：
10.1002/cctc.201902087
复制
发表时间：
2019
期刊：
影响因子：
4.5
通讯作者：
Xixiang Zhang
中科院分区：
文献类型：
--
作者：
Yang Hu;Liu Zhu;彭勇;Jiecai Fu;Xia Deng;Junwei Zhang;Hong Zhang;Chaoshuai Guan;Abdul Karim;Xixiang Zhang
了解碳纳米管的成核和生长过程对于指导工业上高效、可控地合成碳纳米管具有重要意义。然而，控制碳纳米管形成的内在机制仍然存在争议。在这里，使用原位透射电子显微镜（TEM），我们展示了在原子分辨率下从Co2C催化剂纳米颗粒（NP）动态催化生长多层石墨微晶和单壁碳纳米管（SWCNT）。解离的碳原子分别通过表面扩散和体扩散到达小纳米颗粒和大纳米颗粒表面的成核位置。这两种不同的扩散模式被发现是生长单壁碳纳米管（SWCNT）或多层石墨微晶的必要先决条件。小的纳米颗粒利用晶体自旋转来暴露（111）面以有效地捕获碳原子，而大的纳米颗粒利用（111）面上的自重塑来提供原子台阶作为活性成核位点。密度泛函理论（DFT）计算表明，观察结果是在良好的协议与石墨结构的生长机制，涉及晶面的优先选择性。我们的研究结果可能开辟了调整钴基催化剂颗粒的尺寸和晶体取向的可能性，以有效地合成高质量的SWCNTs。
Understanding the nucleation and growth process of carbon nanotubes (CNTs) is important for guiding their efficient and controllable synthesis in industry. However, the intrinsic mechanism that controls the formation of carbon nanotubes is still controversial. Here, using in‐situ transmission electron microscopy (TEM), we demonstrate the dynamic catalytic growth of multilayered graphite crystallites and single‐walled carbon nanotubes (SWCNTs) from the Co2C catalyst nanoparticles (NPs) at the atomic resolution. The dissociative carbon atoms arrive at the nucleation sites on the surface of small and large NPs by the surface and bulk diffusion, respectively. These two different diffusion modes are found to be the essential prerequisite for growing single‐walled carbon nanotubes (SWCNTs) or multilayered graphite crystallites. The small NPs utilize crystal self‐rotation to expose the (111) plane for efficiently capturing carbon atoms, while the large NPs use self‐reshaping on (111) facets to provide atomic steps as active nucleation sites. Density functional theory (DFT) calculations indicate that the observations are in good agreement with the growth mechanism of graphite structures involving the preferential selectivity of crystal facets. Our results may open up the possibility of adjusting the size and crystal orientation of cobalt‐based catalyst particles to efficiently synthesize the SWCNTs with high quality.