Abstract Efficient and affordable electrocatalysts for reversible oxygen reduction and oxygen evolution reactions (ORR and OER, respectively) are highly sought-after for use in rechargeable metal-air batteries. However, the construction of high-performance electrocatalysts that possess both largely accessible active sites and superior ORR/OER intrinsic activities is challenging. Herein, we report the design and successful preparation of a 3D hierarchically porous graphene framework with interconnected interlayer macropores and in-plane mesopores, enriched with pyridinic-nitrogen-cobalt (pyri-N-Co) active sites, namely, CoFe/3D-NLG. The pyri-N-Co bonding significantly accelerates sluggish oxygen electrocatalysis kinetics, in turn substantially improving the intrinsic ORR/OER activities per active site, while copious interlayer macropores and in-plane mesopores enable ultra-efficient mass transfer throughout the graphene architecture, thus ensuring sufficient exposure of accessible pyri-N-Co active sites to the reagents. Such a robust catalyst structure endows CoFe/3D-NLG with a remarkably enhanced reversible oxygen electrocatalysis performance, with the ORR half-wave potential identical to that of the benchmark Pt/C catalyst, and OER activity far surpassing that of the noble-metal-based RuO2 catalyst. Moreover, when employed as an air electrode for a rechargeable Zn-air battery, CoFe/3D-NLG manifests an exceedingly high open-circuit voltage (1.56 V), high peak power density (213 mW cm−2), ultra-low charge/discharge voltage (0.63 V), and excellent charge/discharge cycling stability, outperforming state-of-the-art noble-metal electrocatalysts.

中文翻译：

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富含吡啶-氮-钴活性位点的3D分层宏观/介孔石墨烯框架作为可充电锌空气电池的高效可逆氧电催化剂

摘要 用于可逆氧还原和析氧反应（分别为 ORR 和 OER）的高效且价格合理的电催化剂在可充电金属-空气电池中备受追捧。然而，构建具有大量可接近的活性位点和优异的 ORR/OER 内在活性的高性能电催化剂具有挑战性。在此，我们报告了具有互连层间大孔和面内介孔的 3D 分层多孔石墨烯框架的设计和成功制备，该框架富含吡啶-氮-钴（pyri-N-Co）活性位点，即 CoFe/3D-NLG . pyri-N-Co 键合显着加速了缓慢的氧电催化动力学，进而显着提高了每个活性位点的固有 ORR/OER 活性，而大量的层间大孔和面内中孔能够在整个石墨烯结构中实现超高效的传质，从而确保可接近的 pyri-N-Co 活性位点充分暴露于试剂。这种坚固的催化剂结构使 CoFe/3D-NLG 具有显着增强的可逆氧电催化性能，ORR 半波电位与基准 Pt/C 催化剂相同，OER 活性远远超过贵金属-基RuO2催化剂。此外，当用作可充电锌空气电池的空气电极时，CoFe/3D-NLG 表现出极高的开路电压（1.56 V）、高峰值功率密度（213 mW cm-2）、超低电荷/放电电压（0.63 V）和优异的充/放电循环稳定性，优于最先进的贵金属电催化剂。