Construction of Fe/Co–N4 Single-Atom Sites for the Oxygen Reduction Reaction in Zinc–Air Batteries

Insight into the modulation effect of oxygen reduction reaction (ORR) active centers is of profound significance but remains a great challenge. Here, we designed Co, Fe dual-metal single-atom sites (CoFe-DSAs/NC) uniformly anchored on nitrogen-doped multiwalled carbon nanotubes for boosting ORR performance through regulating the 4d electronic orbitals of the Co–N4 active site. Mechanism studies revealed that for the first time the neighboring Fe–N4 atomic sites were able to regulate the d-band center of Co–N4 single-atom active centers while maintaining the balance of adsorption–desorption affinity for O2 and oxygen-containing species on Co–N4, thereby resulting in a superior ORR performance with a positive half-wave potential (0.90 V vs RHE). The assembled zinc–air battery based on CoFe-DSAs/NC exhibited an increased open-circuit voltage (1.48 V) and an elevated specific capacity (782.33 mAh·g–1). The work provides a new clue for reasonably designing high-performance ORR catalysts through adjusting the d-band center of active sites.