Rational design and facile synthesis of highly active and stable electrocatalysts for oxygen reduction reaction (ORR) are crucial in the field of metal-air batteries. Here, we present a facile two-stage thermal synthesis of Fe-N codoped porous carbon (Fe-N/C) with abundant Fe-N_x active sites and mesopores from Fe-doped ZIF-8 precursors. The first-stage preheating treatment of the Fe-doped ZIF-8 precursors before the second-stage carbonization is the key to boost the coordination between the doped Fe and N-containing ligands, which contributes to a higher N content and more Fe-N_x sites in the final carbonized product. Besides, the preheating and Fe-doping both affect the morphology, porous structure, and catalytic performance of the fabricated Fe-N/C. The optimized Fe-N/C catalyst exhibits an outstanding ORR catalytic performance with a half-wave potential of 0.88 V and limiting current density of 6.0 mA cm^–2 in 0.1 M KOH. A Mg-air battery assembled with a neutral electrolyte using the optimized Fe-N/C catalyst as the cathode exhibits an excellent power density of 72 mW cm^–2 at 0.72 V. This developed two-stage synthesis strategy is facile, and the preheating stage could be integrated into any carbonization process as an intermediate step for the fabrication of various metal, N codoped carbon materials with enhanced electrocatalytic performance.

中文翻译：

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Fe-N _x富集Fe-N配位沸石咪唑酸盐骨架的碳微多面体，具有增强的Fe-N配位，可进行有效的氧还原反应

氧还原反应（ORR）的高活性和稳定电催化剂的合理设计和简便合成对于金属空气电池领域至关重要。在这里，我们介绍了一个简单的两步热合成Fe-N共掺杂多孔碳（Fe-N / C）的方法，该工艺具有丰富的Fe-N _x活性位和中孔，这些元素均来自Fe掺杂的ZIF-8前驱体。在第二阶段碳化之前对掺铁的ZIF-8前体进行第一阶段的预热处理是提高掺杂的铁与含氮配体之间配位的关键，这有助于更高的N含量和更多的Fe-N _X最终碳化产品中的位置。此外，预热和铁掺杂都影响所制备的Fe-N / C的形貌，多孔结构和催化性能。经过优化的Fe-N / C催化剂具有出色的ORR催化性能，在0.1 M KOH中的半波电势为0.88 V，极限电流密度为6.0 mA cm ^–2。以优化的Fe-N / C催化剂为阴极，与中性电解液组装而成的Mg-air电池在0.72 V电压下具有72 mW cm ^-2的出色功率密度。这种发达的两步合成策略很容易实现，并且可以预热该阶段可以集成到任何碳化过程中，作为制造具有增强的电催化性能的各种金属，N共掺杂碳材料的中间步骤。