Isolated iron single-atom sites for oxygen reduction derived from a porphyrin-based carbon sphere by a polymerization-coordination-pyrolysis strategy

Metal isolated single-atom site (ISAS) catalysts serving as promising candidates to substitute nano-catalysts have attracted extensive interest in catalysis. Herein, we prepared Fe, Co and Ni-ISASs, anchored on N-doped carbon (CN) derived from a porphyrin-based carbon sphere by a polymerization-coordination-pyrolysis strategy, much simpler and cheaper than conventional methods to prepare metal ISASs derived from metal-porphyrin-based precursors. The Fe-ISAS/CN catalyst exhibited excellent catalytic performance for alkaline oxygen reduction reaction (ORR), with a half-wave potential of 0.881 V vs. RHE, 36 mV more positive than that of commercial 20 wt% Pt/C, with good stability and methanol tolerance. Besides, Fe-ISAS/CN also exhibited better reactivity and stability for Zn-air batteries. This strategy effectively avoided the usage of expensive commercial metal-porphyrin-based monomers or the complicated and time-consuming procedure during the manual synthesis and purification of metal-porphyrin-based monomers, which will provide inspiration to rationally design metal ISAS catalysts derived from metal-porphyrin-based precursors as promising candidates for Pt-based catalysts for both the ORR and Zn-air batteries.