Fig. 3: Structure of FeN₄O₂-SACs.

a⁵⁷ Fe Mössbauer spectrum. b Normalized XANES spectra of FeN₄O₂-SACs and reference samples (Fe Foil, Fe₂O₃, Fe₃O₄). c EXAFS fitting in R space. d–g Wavelet transformation of Fe Foil (d), FeN₄O₂-SACs (e), Fe₂O₃ (f), and Fe₃O₄ (g). Source data are provided as a Source Data file.