Relay Catalysis of Multi-Sites Promotes Oxygen Reduction Reaction

The two-electron pathway to form hydrogen peroxide (H₂O₂) is undesirable for the oxygen reduction reaction (ORR) in iron and nitrogen doped carbon (Fe–N–C) material as it not only lowers the catalytic efficiency but also impairs the catalyst durability. In this study, a relay catalysis pathway is designed to minimize the two-electron selectivity of Fe–N–C catalyst. Such a design is achieved by introducing two other sites, that is, MnN₄ site and α-Fe(110) face. A combination of transmission electron microscopy image and X-ray absorption spectra verify the three site formation. Electrochemical test coupled with post-treatment confirm the improvement of MnN₄ site and α-Fe(110) face on catalyst performance. Theoretical calculation proposes a relay catalysis pathway of three sites, that is, H₂O₂ released from the FeN₄ site migrates to the MnN₄ site or α-Fe(110) face, on which the captive H₂O₂ is further reduced to H₂O. The relay catalysis pathway positioned the as-prepared catalyst among the best ORR catalysts in both aqueous electrode and alkaline direct methanol fuel cell test. This study examples an interesting relay catalysis pathway of multi-sites for the ORR, which offers insights into the design of efficient electrocatalysts for fuel cells or beyond.