fig1

Figure 1. Comparison of morphology and porosity of precursors and catalysts. (A) synthetic scheme; SEM images of (B) ZIF-L NA and (C) Fe-N-C NA; HAADF-STEM and EDS mapping images of (D) ZIF-L NA and (E) Fe-N-C NA; TEM and EDS mapping images of (F) ZIF-L bulk and (G) Fe-N-C bulk. SEM: Scanning electron microscope; NA: nano-assembly; HAADF-STEM: high-angle annular dark-field scanning transmission electron microscopy; EDS: energy dispersive spectrometer; TEM: transmission electron microscopy.