Fig. 2: The configuration of active sites in the electrocatalysts.

a HAADF-STEM images of the Fe-N-C. b HAADF-STEM images of the Fe-N-CCVM. c Normalized XANES spectra of Fe K-edge for Fe foil, Fe-N-CCVM, Fe-N-C, Fe2O3 and FePc. d The k3-weighted EXAFS spectra for Fe foil, Fe-N-CCVM, Fe-N-C and FePc. e EXAFS fitting results of Fe foil, Fe-N-CCVM, Fe-N-C. f N K-edge XANES spectra of Fe-N-CCVM and Fe-N-C. Wavelet transform of Fe K-edge EXAFS data for (g) Fe-N-CCVM, (h) Fe-N-C and (i) Fe foil.