Co single-atom (Co_SA) catalysts of the CoN₄ moiety usually show an unsatisfactory oxygen reduction reaction (ORR) activity due to poor O₂ activation. Herein, we open up a novel strategy to improve the ORR activity of the Co_SA–N–C catalyst. Its structure was first built to involve the deformed CoN₄ site and enhance mesoporosity. Secondly, Co nanoparticle and CoN₄ (Co_NP–CoN₄) composite sites were created in the catalyst and the total CoN₄ density was effectively replenished. Finally, the concave nanocube-like catalyst showed an excellent ORR performance in the RDE test (E_1/2 = 0.83 V vs. RHE, 12 mV loss after 50K cycles) in acidic media. Furthermore, the catalyst showed a high power density in the fuel cell test (P_max-H₂–O₂ ca. 1.207 W cm⁻²). Theoretical studies agree with experimental findings that both Co_NP–CoN₄ composite sites and deformed CoN₄ can enhance O₂ activation. In addition, the inhibited H₂O₂ formation and the enhanced adsorption of radical oxygen species due to Co_NP–CoN₄ composite sites can greatly reduce carbon layer erosion, resulting in improved performance in both activity and durability. Our finding not only provides a novel strategy to develop ORR catalyst but also brings new insights into ORR fundamentals.

中文翻译：

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纳米几何变形与协同Co纳米粒子——质子交换膜燃料电池的Co-N4复合位点

CoN ₄部分的Co单原子（Co _SA）催化剂通常由于O ₂活化差而表现出不令人满意的氧还原反应（ORR）活性。在此，我们开辟了一种提高 Co _SA -N-C 催化剂ORR 活性的新策略。其结构首先构建为涉及变形的 CoN ₄位点并增强介孔性。其次，在催化剂中产生了Co纳米颗粒和CoN ₄ (Co _NP -CoN ₄ )复合位点，有效地补充了总的CoN ₄密度。最后，凹面纳米立方体催化剂在 RDE 测试中表现出优异的 ORR 性能（E _1/2= 0.83 V vs. RHE，50K 循环后损失 12 mV）在酸性介质中。此外，该催化剂在燃料电池测试中显示出高功率密度（P _max -H ₂ -O ₂ ca. 1.207 W cm ^-2）。理论研究和实验研究结果一致，这两个共同_NP -CON _4个复合位点和变形的CoN ₄可增强Ò ₂活化。此外，Co _NP –CoN ₄抑制了 H ₂ O _{2 的}形成并增强了自由基氧物种的吸附复合材料位点可以大大减少碳层侵蚀，从而提高活性和耐久性方面的性能。我们的发现不仅提供了一种开发 ORR 催化剂的新策略，而且还为 ORR 的基本原理带来了新的见解。