Abstract
Transition of metal-to-metal carbide plays a key role in heterogeneous catalysis. We confined nickel nanocrystals in single-walled carbon nanotubes, stimulated delivery of carbon atoms by the 80 keV electron beam, and imaged the entire carbonization process by time-resolved aberration-corrected transmission electron microscopy at the atomic scale. Metal nanocrystal Ni(40) progressively capturing carbon atoms evolved from pure metal to Ni(40)C(20) and then to Ni(40)C(40). The carbonization is accompanied by changes in the structure of the crystal, including a two-dimensionalization process, at the Ni(40)C(40) stage. This work provides valuable insights into the atomic mechanism of metal carbide formation, which may help to develop stable catalysts and provide a reliable route for synthesizing metal-based two-dimensional materials.