fig3

Figure 3. (A) XRD patterns, (B) Raman spectra, (C) XPS envelopes of (C) Co 2p and (D) N 1s, and (E) proportion of different N species determined by XPS analysis of Co-N/C and Co-N/C-U. (F) Co K-edge XANES spectra, (G) Relationship between the valence states of Co and energy position of XANES spectra, and (H) FT k³-weighted Co K-edge EXAFS spectra of Co-N/C, Co-N/C-U, and reference samples. (I and J) Co K-edge EXAFS curve fitting results R space, (K) Wavelet transform (WT) of Co-N/C and Co-N/C-U, and (L) CO₂-TPD profiles of Co-N/C and Co-N/C-U.