fig4

Figure 4. (A) Preparation process and proposed formation mechanisms of Co@DMOF; (B) AC HAADF-STEM; (C) FT-EXAFS curves of Co foil and Co@DMOF-900. The (A-C) are quoted with permission from Yuan et al.^[60]; (D) Schematic of the synthetic process for the Ni SAs@S/N-FCS; (E) HAADF-STEM and (F) AC HAADF-STEM images of Ni SAs@S/N-FCS; (G) Top view image of 3D atom-overlapping Gaussian-function fitting mapping; (H) FT EXAFS spectra of NiO, Ni foil, and Ni SAs@S/N-FCS. The (D-H) are quoted with permission from Zhao et al.^[61]; (I) Schematic illustration of the synthesis process for Fe-SA/NC catalysts; (J) AC-HADDF STEM and (K) FT-EXAFS images of Fe-SA/NC catalysts. The (I-K) are quoted with permission from Tian et al.^[22]. AC HAADF-STEM: Aberration-corrected high-angle annular dark field scanning transmission electron microscopy; FT-EXAFS: Fourier transform of extended X-ray absorption fine structure.