fig12

Figure 12. (A) Schematic showing the two-step synthesis of Fe₂-N-C; (B) HAADF-STEM images and (C) K³-weighted χ(k) function of the EXAFS spectra of Fe₂-N-C; (D) LSV curves in O₂-saturated 0.5 M H₂SO₄ solution at a sweep rate of 10 mV s^-1 and a rotation speed of 1,600 rpm; (E) durability test results of Fe₂-N-C after 5,000, 10,000 and 20,000 cycles (A-E reproduced with permission from Elsevier, copyright 2019)^[158]; (F) Schematic showing the synthesis of the Fe₂/NC catalyst; (G) aberration-corrected HAADF-STEM image of Fe₂/NC (white circles delineate the diatomic Fe₂ sites); (H) corresponding EXAFS fitting curves of Fe₂/NC in R space; LSV curves of (I) NC, Fe₂Cl_X/NC, Fe₂/NC and Pt/C at 1,600 rpm in O₂-saturated 0.1 M KOH and (J) Fe₂/NC before and after the stability test (F-J reproduced with permission from Wiley-VHC, copyright 2024)^[159]. HAADF-STEM: High-angle annular dark field-scanning transmission electron microscopy; EXAFS: extended X-ray absorption fine structure; LSV : linear sweep voltammetry.