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As one type of bifunctional oxygen electrocatalyst for Zn-air battery, herein, FeNi alloy was successfully embedded into N -doped carbon with tailored architectures by integrating MOF precursor method and polymer coating/encapsulation strategy. The content of Fe in primary precursor has been proven to be able to obviously affect the morphology of the final catalyst. Benefiting from the mature active site (e.g. FeNi alloy) and the stable carbon matrix, a series of catalysts exhibited good performance towards ORR and OER. Of great significance, a particular ratio of Fe/Ni happened to be able to catalyze the growth of 1D bamboo-like carbon nanotubes, giving rise to a conductive network to diffuse ORR/OER-relevant species. Apparently, a low discharge-charge voltage gap (1.1 V) was acquired in a liquid Zn–air battery with 1.5FeNi@NCNT air cathode. Moreover, the solid-state Zn-air battery assembled on it also displayed a high open circuit voltage (1.38 V) and yielded a high power density of 81 mW cm−2 at 0.83 V. This would leverage a choice to tailor carbon geometry of FeNi alloy-based active sites for ORR/OER and further serve for devices of practical significance. [ABSTRACT FROM AUTHOR]

Optimized catalysts are attractive from the standpoint of energy storage and conversion. Herein, a pearl necklace fibrous carbon catalyst with Fe–N/Fe–P dual active sites (Fe–P/NHCF) is fabricated via carbonization–phosphidation of metal–organic framework (MOF)/polyacrylonitrile nanofibers. Benefiting from Fe–N/Fe–P doping‐induced active sites, accompanied by particular hierarchical porous merit and a 1D necklace network to facilitate the oxygen reduction reaction (ORR), it exhibits a half‐wave potential of 0.82 V in alkaline medium and outperforms commercial Pt/C in terms of stability in acid medium. Furthermore, a low voltage gap (1.04 V) is acquired in a liquid Zn–air battery with Fe–P/NHCF as the cathode. Meanwhile, the portable solid‐state Zn–air battery displays an open circuit voltage of 1.32 V and a power density of 42 mW cm−2. This strategy puts forward a protocol to develop tailored geometry with dual active sites for ORR in alkaline/acid media, which is expected to promote devices of practical significance. [ABSTRACT FROM AUTHOR]

Non‐precious metal nanocomposite has attracted extensive attention as an effective catalyst for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, hierarchically porous N‐doped carbon nanofibers supported Fe3C/Fe nanoparticles (denoted as Fe/N‐HCNFs) have been successfully fabricated. The synthesis involved the successive steps of electrospun polyacrylonitrile (PAN) and zeolitic imidazolate framework (ZIF‐8) nanofiber, surface functionalization of tannic acid (TA), coordination with ferric salt and carbonization. The obtained Fe/N‐HCNFs exhibited enhanced electrocatalytic performance for both ORR and OER. Furthermore, Fe/N‐HCNFs delivered a higher power density and an excellent long‐term stability when applied in a constructed Zn‐air battery, which illustrated its outstanding prospects for energy storage and conversion. The N‐doped carbon nanofibers supported Fe3C/Fe nanoparticles (denoted as Fe/N‐HCNFs) have been successfully fabricated through the successive steps of electrospinning, tannic acid coating, metal deposition and carbonization. The hierarchically porous nanostructure with well‐dispersed electroactive sites endowed Fe/N‐HCNFs efficient catalytic ability for oxygen reduction and oxygen evolution reactions.When applied in a constructed Zn‐air battery, Fe/N‐HCNFs delivered a higher power density and excellent long‐term stability. [ABSTRACT FROM AUTHOR]