First-row transition metal-containing bifunctional electrocatalysts are essential in developing metal–air batteries with high cycling efficiency. Core–corona structured porous N-doped carbon with tangled carbon nanotubes was synthesised by pyrolysing CoFe₂O₄ encapsulated ZIF-8. Structural characterisation indicates the presence of the CoFe metal alloy, which catalyses the formation of nanotubes. Besides, the CoFe alloy nanoparticles encapsulated by graphitic carbon improve the oxygen reduction and evolution reactions, corroborated by control samples. The bifunctional activity of the catalysts was analysed using the zinc–air battery, which exhibits an excellent power density of 162 mW cm⁻² and a high specific capacity of 900 mA h g_Zn⁻¹. The real-time application was evaluated using the solid-state zinc–air battery, which exhibits the highest open circuit potential of 1.53 V. The CoFe alloy encapsulated N-doped carbon should be an efficient air-electrode catalyst for metal–air battery application.

中文翻译：

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用于可充电锌空气电池应用的核-电晕结构双功能含氮钴铁氧体碳纳米管的活性位点探索

第一排含过渡金属的双功能电催化剂对于开发高循环效率的金属-空气电池至关重要。通过热解CoFe ₂ O ₄封装的ZIF-8合成了具有缠结碳纳米管的核冠结构多孔N掺杂碳。结构表征表明存在 CoFe 金属合金，其催化纳米管的形成。此外，石墨碳封装的 CoFe 合金纳米颗粒改善了氧还原和析出反应，这一点已得到对照样品的证实。使用锌空气电池分析了催化剂的双功能活性，该电池表现出162 mW cm ^{-2的优异功率密度和900 mA hg} _Zn ^-1的高比容量。使用固态锌空气电池对实时应用进行了评估，该电池的最高开路电位为 1.53 V。CoFe 合金封装的 N 掺杂碳应该是金属空气电池应用的有效空气电极催化剂。