Fig. 2: Morphological and structural characterizations.

a HAADF-STEM image of Co-N4-NP. b Co K-edge XANES and c FT-EXAFS spectra of Co-N4, Co-N4-NP and reference samples. d Comparison between the experimental XANES spectrum and theoretical one calculated with the depicted structures of Co-N4-NP. (insert is the correlative atomic structures). e Co K-edge WT-EXAFS contour plots for Co-N4, Co-N4-NP and reference samples.