fig3

Figure 3. (A) Cl 2p XPS spectra of Co-N₄-C and Co-N₄Cl-C; (B) Co-K-edge XANES spectra of samples and references (the inset shows the magnified pre-edge XANES region); (C) The determined Co K-edge positions and oxidation statuses of Co in the Co-N₄Cl-C and Co-N₄-C; (D) FT of the EXAFS spectra of samples and references. First-shell fitting of FT of EXAFS spectra for (E) Co-N₄-C and (F) Co-N₄Cl-C. EXAFS spectra were fitted using the FEFF 6.0 code (the insets show the structure of the Co-N₄-C and Co-N₄Cl-C; the balls in gray, blue, pink, and green correspond to C, N, Co, and Cl atoms, respectively); (G) WT of samples and references. XPS: X-ray photoelectron spectroscopy; XANES: X-ray absorption near-edge structure; EXAFS: extended X-ray absorption fine structure; FT: Fourier transform; FEFF: full multiple scattering; WT: wavelet-transformed.