The rational exploitation of non-precious metal catalyst with high activity, strong durability and low cost for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is of vital importance for metal–air batteries. Herein, a composite of Co3O4 nanoparticles confined in three-dimensional (3D) N-doped porous carbon (Co-NpCs) was prepared by a simple freeze-drying and in situ pyrolysis method. The effect of different dosages of Co(NO3)2 on the catalytic performance was discussed. The Co-NpC-12% exhibits the best catalytic performance (E1/2 = 0.78 V, better stability than 20% Pt/C) in ORR and in OER among all the as-synthesized samples. Furthermore, it also exhibits the best bifunctional activity (ΔE = 0.849 V). The excellent properties of Co-NpCs are mainly due to the synergy between Co3O4 and carbon. Firstly, a high Co3O4 loading amount can boost the defect level of the N-doped hierarchical porous carbon and expose more active sites. Secondly, the unique in situ pyrolysis guarantees a large-area contact between Co3O4 and carbon as well as a strong C–O–Co bonding, which promotes charge transfer, avoids the peeling of Co3O4 nanoparticles and effectively improves the stability of the material. This work is expected to offer a feasible strategy to produce metal oxide/carbon nanocomposite and push forward the development of bifunctional electrocatalyst with high activity and stability.

中文翻译：

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原位合成限制在 3D 氮掺杂多孔碳中的 Co3O4 纳米粒子作为一种高效的双功能氧电催化剂

合理开发活性高、耐久性强、成本低的非贵金属催化剂用于氧还原反应（ORR）和析氧反应（OER）对金属-空气电池至关重要。在此，通过简单的冷冻干燥和原位热解方法制备了限制在三维 (3D) N 掺杂多孔碳 (Co-NpCs) 中的 Co3O4 纳米粒子复合材料。讨论了不同Co(NO3)2用量对催化性能的影响。在所有合成样品中，Co-NpC-12% 在 ORR 和 OER 中表现出最好的催化性能（E1/2 = 0.78 V，稳定性优于 20% Pt/C）。此外，它还表现出最佳的双功能活性（ΔE = 0.849 V）。Co-NpCs 的优异性能主要归功于 Co3O4 和碳之间的协同作用。首先，高 Co3O4 负载量可以提高 N 掺杂分级多孔碳的缺陷水平并暴露更多活性位点。其次，独特的原位热解保证了 Co3O4 与碳之间的大面积接触以及强大的 C-O-Co 键合，促进了电荷转移，避免了 Co3O4 纳米颗粒的剥离，有效提高了材料的稳定性。该工作有望为制备金属氧化物/碳纳米复合材料提供一种可行的策略，并推动具有高活性和稳定性的双功能电催化剂的发展。避免了Co3O4纳米颗粒的剥离，有效提高了材料的稳定性。该工作有望为制备金属氧化物/碳纳米复合材料提供一种可行的策略，并推动具有高活性和稳定性的双功能电催化剂的发展。避免了Co3O4纳米颗粒的剥离，有效提高了材料的稳定性。该工作有望为制备金属氧化物/碳纳米复合材料提供一种可行的策略，并推动具有高活性和稳定性的双功能电催化剂的发展。