Fig. 1: Preparation and characterization of catalyst.

a Schematic illustration for the synthesis of Fe-pdN-C(O), Fe-poN-C(O) and Fe-poN-C/Fe. b XRD patterns of Fe-pdN-C(O), Fe-poN-C(O) and Fe-poN-C/Fe. (c) Large-field view, (d) magnified view of HAADF-TEM, (e, f) aberration-corrected HAADF-STEM, and (g) EDS mapping of Fe-poN-C/Fe.