Impact of heterometallic cooperativity of iron and copper active sites on electrocatalytic oxygen reduction kinetics

Kato, Masaru*; Fujibayashi, Natsuki*; Abe, Daiki*; Matsubara, Naohiro*; Yasuda, Satoshi   ; Yagi, Ichizo*

Fe-N-C oxygen reduction reaction catalyst is a key materials in polymer electrolyte fuel cell. However, the many Fe-N-C electrocatalysts still suffer from product selectivity due to the production of HO as the byproduct. In this work, we synthesized an ORR electrocatalyst of Cu, Fe, and N-doped carbon nanotubes. This heterobimetallic catalyst showed the selective four electron reduction of O to HO. Kinetic analysis of the electrocatalytic ORR and hydrogen peroxide reduction reaction in acidic media revealed that Cu, Fe-N-doped catalyst showed two orders of magnitude higher rate constants for the direct four electron reduction of O to HO than those for the two electron reduction of O to HO, whereas a monometallic Fe-N-doped catalyst showed the same order of magnitude, indicating that the heterometallic cooperativity had a drastic impact on the ORR kinetics.