fig8

Figure 8. (A) Schematic and (B) HAADF-STEM image of OP-Fe-NC; (C) Fourier transformed EXAFS spectra of OP-Fe-NC catalysts; (D) corresponding quantitative fittings of the EXAFS spectra in R space. Inset shows the corresponding EXAFS fitting in K space; (E) Comparison between the experimental and theoretical X-ray absorption near-edge structure (XANES) spectra. Inset is a schematic of the interfacial model of OP-Fe-NC; (F) LSV curves; (G) polarization and power density curves of H₂-O₂ fuel cells with OP-Fe-NC and 20 wt% Pt/C; (H) Bader charge transfers and adsorption energies of the intermediates and (I) partial densities of states (PDOSs) of the Fe d bands in Fe-NC, Fe-ONC, and Fe-ONCS; (J) Gibbs free energy profiles of the ORR at U = 0 and 1.23 V (A-J reproduced with permission from the American Chemical Society, copyright 2023)^[129]. HAADF-STEM: High-angle annular dark field-scanning transmission electron microscopy; EXAFS: extended X-ray absorption fine structure; LSV: linear sweep voltammetry.