Boosting the bifunctional oxygen electrocatalytic performance of atomically dispersed Fe site via atomic Ni neighboring

[Display omitted] •Atomically dispersed binary NiFe-NC with tunable Ni/Fe ratios were fabricated.•The NiFe-NC with an optimal Ni/Fe ratio of 66:34 contained rich Ni-Fe dual-site.•Dual-site mode of Ni-Fe was beneficial for more charge localized over Ni/Fe sites.•Ni66Fe34-NC showed excellent ORR, OER, and rechargeable Zn-air battery performance.•DFT and in-situ Raman studies suggested Fe in Ni-Fe dimer responded for ORR/OER. Atomically dispersed metal-nitrogen-carbon complexes on carbon supports have drawn tremendous attention in the electrocatalysis fields. Herein, we managed the synthesis of atomically dispersed binary NixFe100-x-NC (x = 0–100) materials with tunable Ni/Fe ratios and investigated their underneath synergy effects for the enhancement of oxygen reduction (ORR) and oxygen evolution reactions (OER). EXAFS revealed the abundant presence of Ni(N3)-Fe(N3)-Cn moieties in Ni66Fe34-NC sample. XPS fine scans indicated deep synergy of dual-site Ni/Fe that favored more charge localized over Ni/Fe sites. Electrochemical measurments showed that the Ni66Fe34-NC delivered a very high ORR half-wave potential (E1/2) of 0.85 V and a low OER overpotential of 467 mV at ∼10 mA cm−2 (Ej=10). The Fe site with Ni neighboring, as suggested by DFT simulations and in-situ Raman, was the responsible site for both ORR and OER. Furthermore, the Ni66Fe34-NC-assembled Zn-air battery afforded large specific power density and extraordinary cycling stability.