Simply embedding α-Fe2O3/Fe3O4 nanoparticles in N-doped graphitic carbon polyhedron layered arrays as excellent electrocatalyst for rechargeable Zn-air battery

•α-Fe2O3/Fe3O4 nanoparticles were simply embeded in N-doped graphitic carbon arrays.•Multiple active sites of Fe2+/Fe3+, oxygen vacancy and pyridinic-N were obtained.•Multicomponent synergy endowed the catalysts high intrinsic activity and stability.•Unique layered array structure supplied short path for charge and mass transfer.•The catalyst has higher electrocatalytic activities than Pt/C and RuO2. Hybrids of α-Fe2O3/Fe3O4 nanoparticles embedded in N doped graphitic carbon polyhedron layered arrays (FeOx/NCLA) were simply constructed by pyrolyzing the composite precursor of NH2-MIL-101(Fe) (a metal organic framework, MOF) and glycylglycine. The experimental and calculated results reveal that the obtained catalysts exhibited multiple active components, synergistic heterojunction effect, high BET surface areas and conductivity, and consequently greatly improved intrinsic electrocatalytic activities and kinetics for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). As the results, the optimized catalyst FeOx/NCLA-1.2 exhibited positive half-wave potential of 0.846 V for ORR and only 218 mV of overpotential (at 10 mA/cm2) for OER in alkaline electrolyte, which is superior than Pt/C (20 %) and RuO2, respectively. The Zn-air battery (ZAB) employing the FeOx/NCLA-1.2 as electrocatalyst obtained a peak power density of 104.3 mW·cm−2, a specific capacity of 840 mAh·gZn-1 and an energy density of 890 Wh·kgZn-1, which is also much higher than that for the noble metal based one. The catalyst is promised to be applied in water electrolysis, fuel cells and metal-air batteries.