Efficient,　robust　and　cost-effective　bifunctional　oxygen　electrocatalysts　for　oxygen　reduction　reaction　(ORR)　and　oxygen　evolution　reaction　(OER)　are　of　vital　importance　to　the　widespread　utilization　of　Zn-air　batteries.　Here　we　report　the　fabrication　of　a　bubble-like　N,S-codoped　porous　carbon　nanofibers　with　encapsulated　fine　Fe/Fe5C2　nanocrystals　(∼　10　nm)　(FeNSCs)　by　a　facile　one-pot　pyrolysis　strategy.　The　novel　FeNSC　nanostructures　with　high　Fe　content　(37.3　wt.%),　and　synergetic　N　and　S　doping　demonstrate　remarkable　ORR　and　OER　catalytic　activities　in　alkaline　condition.　Particularly　for　ORR,　the　optimal　FeNSC　catalyst　exhibits　superior　performance　in　terms　of　current　density　and　durability　in　both　alkaline　and　acidic　media.　Moreover,　as　catalysts　on　the　air　electrodes　of　Zn-air　batteries,　the　optimal　FeNSCs　show　a　high　peak　power　density　of　59.6　mW/cm2　and　extraordinary　discharge-charge　cycling　performance　for　200　h　with　negligible　voltage　gap　change　of　only　8%　at　current　density　of　20　mA/cm,　surpassing　its　noble　metal　counterpart　(i.e.　Pt).　The　impressive　battery　stability　can　be　attributed　to　favorable　electron　transfer　resulting　from　appropriate　graphitization　of　the　bubble-like　carbon　nanofibers　and　thorough　protection　of　Fe/Fe5C2　nanoparticles　by　carbon　wrapping　to　prevent　oxidation,　agglomeration　and　dissolution　of　Fe　nanoparticles　during　battery　cycling.　The　present　FeNSC　catalyst,　which　is　highly　active,　robust　yet　affordable,　shows　promising　prospects　in　large-scale　applications,　such　as　metal-air　batteries　and　fuel　cells.　[Figure　not　available:　see　fulltext.]　©　2020,　Tsinghua　University　Press　and　Springer-Verlag　GmbH　Germany,　part　of　Springer　Nature.