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.

用于氧还原反应（ORR）和氧释放反应（OER）的高效，耐用且经济高效的双功能氧电催化剂对于Zn-空气电池的广泛应用至关重要。在这里，我们报道了包裹有细密的Fe / Fe ₅ C ₂的气泡状N，S掺杂多孔碳纳米纤维的制备。纳米单晶（〜10 nm）（FeNSCs）通过一种简单的一锅热解策略。具有高铁含量（37.3 wt。％）的新型FeNSC纳米结构以及协同的N和S掺杂在碱性条件下显示出显着的ORR和OER催化活性。特别是对于ORR，最佳的FeNSC催化剂在电流密度和在碱性和酸性介质中的耐久性方面均表现出优异的性能。此外，作为锌-空气电池的空气电极上的催化剂，最佳的FeNSC表现出59.6 mW / cm ^2的高峰值功率密度出色的放电-充电循环性能200小时，在20 mA / cm的电流密度下，电压间隙变化仅为8％，超过了贵金属（Pt）。令人印象深刻的电池稳定性可归因于气泡状碳纳米纤维的适当石墨化，以及通过碳包裹对Fe / Fe ₅ C ₂纳米颗粒的充分保护，从而防止了电池循环过程中Fe纳米颗粒的氧化，团聚和溶解，从而产生了良好的电子转移。本发明的FeNSC催化剂是高活性，坚固但价格适中的，在诸如金属-空气电池和燃料电池的大规模应用中显示出有希望的前景。