“…1c exhibits metallic Fe (707.3 and 719.9 eV), Fe–N (709.6 and 722.8 eV), Fe 2+ (711.5 and 724.4 eV), as well as Fe 3+ species (714.5 and 728.0 eV). 37,38 Similarly, the Co 2p XPS spectrum in Fig. 1d shows the presence of Co 2p 3/2 (metallic Co at 778.4 eV, Co–N at 780.4 eV, oxidized Co component at 782.3 eV and satellite at 786.5 eV) and Co 2p 1/2 (metallic Co at 794.0 eV, Co–N at 796.2 eV, oxidized Co species at 798.2 eV and satellite at 803.2 eV).…”