fig1

Figure 1. (A-C) TEM images of Co@CNTs under different vision; (D) HR-TEM image of Co@CNTs; (E) Element mapping of Co@CNTs for C, O, Co; (F-H) TEM images of Co SAs/NPs@N-CNTs under different vision; (I) HR-TEM image of Co SAs/NPs@N-CNTs; (J) Element mapping of Co SAs/NPs@N-CNTs for C, O, Co, N. TEM: Transmission electron microscopy; CNTs: carbon nanotubes; HR-TEM: high resolution transmission electron microscope; SAs: single atoms; NPs: nanoparticles.