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[Display omitted] • A highly efficient Fe SAs/NPs@NC catalyst for boosting the ORR is developed. • A synergistic effect stemming from the isolated Fe-N x and metallic Fe is uncovered. • The catalyst showed high ORR activity and stability superior to the commercial Pt/C. • The Zn-air battery exhibits high power density and excellent cycling stability. Herein, a proof-of-concept study on the evaluation of Fe nanoparticles (Fe NPs) encapsulated by nitrogen-doped carbon to Fe single atoms (Fe SAs) for boosting the oxygen reduction reaction (ORR) catalytic activity toward Zn-air batteries was reported. Specifically, unlike Fe SAs encapsulated by nitrogen-doped carbon (Fe SAs@NC), the Fe SAs and Fe NPs co-embedded in nitrogen-doped carbon (Fe SAs/NPs@NC) derived from a pyrolysis and acid dissolution protocols exhibits excellent ORR performance with good stability and remarkable methanol tolerance in alkaline solutions. Combining a series of experimental analyses, the strong interaction between the atomically dispersed Fe-N x and adjacent Fe NPs in altering the electronic structure of isolated Fe-N x sites could weaken the binding energies of the ORR intermediates on Fe SAs/NPs@NC, resulting in an enhanced electrocatalytic kinetics than Fe SAs@NC and Pt/C catalysts. This strategy not only offers a new way for synthesis highly efficient Fe-N/C catalysts toward ORR, but also provides the new insights into the understanding of the mechanism of adjacent Fe NPs encapsulated by nitrogen-doped carbon to Fe SAs sites. [ABSTRACT FROM AUTHOR]