Fig. 2: Characterization of CuSAE.
a A representative TEM image of SiO2@PDA@Cu. Seven images were recorded and show similar results. b A representative TEM image of CuSAE. Images were recorded on three independent samples and show similar results. c A representative EDS element mapping of CuSAE. Three images were recorded and show similar results. d XRD spectrum of CuSAE. e, f XPS spectra of CuSAE; e the C 1s region, f the N 1s region. XPS measurements revealed graphitic-N, pyrrolic-N, and pyridinic-N as dominant nitrogen species in CuSAE. g HAADF-STEM image of CuSAE. White circles indicate single Cu atoms. Three images were recorded and show similar results. h, i X-ray absorption fine structure analysis of CuSAE; h Fourier-transformed EXAFS signal of CuSAE and reference samples; i XANES spectra at Cu K-edge of CuSAE and reference samples. Source data are provided as a Source Data file.
