Dual-atom Co-Fe catalysts for oxygen reduction reaction

Controlled synthesis of dual-atom catalysts (DACs) for heterogeneous catalytic reactions is vital but still demanding. Herein, we construct a novel dual-atom catalyst containing FeN3-CoN3 sites on N-doped graphene nanosheets (CoFe-NG), which exhibits remarkable catalytic performance with a half-wave potential of 0.952 V for oxygen reduction reaction (ORR) and shows higher endurance to methanol/carbon monoxide poisoning and better durability than commercial Pt/C. The assembled Zn-air battery with CoFe-NG as the air electrode delivers a peak power density of 230 mW cm–2 and exhibits negligible change in output voltage at 5 mA cm–2 for 250 h. Theoretical calculations reveal that FeN3-CoN3 sites on N-doped graphene exhibit lower ORR barrier than FeN4 and CoN4 sites, and the rate-limiting step on the former is the transformation of *OH intermediate to H2O, different from the transformation of *O to *OH on the FeN4 site and the transformation of O2 to *OOH on the CoN4 site.