fig3

Figure 3. (A) Schematic illustration of the synthesis of FeN₄ SAC; (B) FT k³-weighted χ(k)-function of the EXAFS spectra at Fe K-edge^[19], Copyright 2023, Springer Nature; (C) Schematic illustration of the synthetic procedure of the SCoNC catalysts; and (D) SEM image of the SCoNC catalyst^[20]. Copyright 2023, Wiley; (E) Schematic of the synthesis process of the Fe-N/P-C catalyst; (F) Enlarged image of Fe-N/P-C, partial single Fe atoms are circled in yellow and EELS atomic spectra of Fe, N, and P elements^[22], Copyright 2023, ACS Publications; (G) Synthesis and morphology of Ni,Fe-SAs/NCs; and (H) BF-STEM image and corresponding HAADF-STEM image^[23]. Copyright 2023, ACS Publications. SAC: Single atom electrocatalyst; EXAFS: extended X-ray absorption fine structure; SEM: scanning electron microscopy; EELS: electron energy loss spectroscopy; NCs: N-doped carbons; BF-STEM: bright field scanning transmission electron microscopy; HAADF-STEM: high-angle annular dark field scanning transmission electron microscopy.