Iron polyphthalocyanine-derived ternary-balanced Fe 3 O 4 /Fe 3 N/Fe-N-C@PC as a high-performance electrocatalyst for the oxygen reduction reaction

The oxygen reduction reaction (ORR) is the cornerstone reaction of the cathode in metal-air batteries; however, slow kinetics requires high-performance catalysts to promote the reaction. Polyphthalocyanine (PPc) has a typical chemical cross-linking structure and uniformly dispersed metal active sites, but its poor activity and conductivity limit its applications as an ORR catalyst. Herein, a manageable and convenient strategy is proposed to synthesize ternary ORR catalysts through the low-temperature pyrolysis of FePPc. The optimal catalyst, Fe 3 O 4 /Fe 3 N/Fe-N-C@PC-2.5, exhibits excellent ORR activity in alkaline solution with a half-wave potential of 0.90 V, which is significantly higher than that of commercial 20% Pt/C (0.84 V). Electrochemical tests and extended X-ray absorption fine structure spectroscopy reveal that the superior ORR activity of Fe 3 O 4 /Fe 3 N/Fe-N-C@PC-2.5 could be ascribed to the balance of its ternary components (i.e., Fe 3 O 4 , Fe 3 N, and Fe-N 4 species). A Zn-air battery incorporating Fe 3 O 4 /Fe 3 N/Fe-N-C@PC-2.5 as an air cathodic catalyst delivers a high open-circuit voltage and peak power density. During galvanostatic discharge, the battery demonstrates a specific capacity of 815.7 mA h g −1 . The facile strategy of using PPc to develop high performance composite electrocatalysts may be expanded to develop new types of catalysts in the energy field.