When carbon-containing species are involved in reactions catalyzed by transition metals at high temperature, the diffusion of carbon on or in catalysts dramatically influences the catalytic performance. Acquiring information on the carbon-diffusion-involved evolution of catalysts at the atomic level is crucial for understanding the reaction mechanism yet also challenging. For the chemical vapor deposition process of single-walled carbon nanotubes (SWCNTs), we recorded in situ the catalyst state (solid and molten) composition as well as near-surface structural and chemical evolution at the cobalt catalyst–tube interface with carbon permeation using aberration-corrected environmental transmission electron microscopy and synchrotron X-ray absorption spectroscopy. The nucleation of SWCNTs was linked with an alternating dissolving and precipitating cycle of carbon in catalysts close to the nucleation site. Understanding the dynamics of carbon atoms in catalysts brings deeper insight into the growth mechanism of SWCNTs and facilitates inferring mechanisms of other reactions. The methodologies developed here will find broad applications in studying catalytic and other processes.

当含碳物质参与高温下过渡金属催化的反应时，碳在催化剂上或催化剂中的扩散会极大地影响催化性能。获取有关在原子水平上涉及碳扩散的催化剂演化的信息对于理解反应机理也具有挑战性至关重要。对于单壁碳纳米管（SWCNT）的化学气相沉积过程，我们就地记录了催化剂状态（固态和熔融态）的组成以及在钴催化剂-管界面处的近表面结构和化学演化以及碳渗透的过程。像差校正环境透射电子显微镜和同步加速器X射线吸收光谱。SWCNT的成核与碳在接近成核位置的催化剂中的交替溶解和沉淀循环有关。了解催化剂中碳原子的动力学特性可以更深入地了解SWCNT的生长机理，并有助于推断其他反应的机理。这里开发的方法将在研究催化和其他过程中找到广泛的应用。