fig3

Figure 3. (A, B) SEM, (C, D), TEM, (E) HRTEM and (F) AC HAADF-STEM images of CoNi-SAs/NC. (G) Co K-edge XANES spectra and (H) Fourier transforms of Co K-edge spectra of CoNi-SAs/NC and CoNi-NPs/NC (inset: the model of Ni-Co dual sites). (I) Schematic illustration of the formation of CoNi-SAs/NC. (J) ORR polarization curves and (K) OER polarization curves of CoNi-SAs/NC and reference samples^[107]. SEM: Scanning electron microscope; HRTEM: high resolution TEM; XANES: X-ray absorption near edge structure; OER: oxygen evolution reaction.