Atomically dispersed metal–nitrogen carbon (M–N–C) catalysts with e¹_g are believed to be very active for the oxygen reduction reaction; however, the activity origin of spin state manipulation is unclear. Here, using Fe–N–C as a model catalyst, we have developed a facile approach to manipulate its spin state from the low-spin to medium-spin state (Fe_SAC–NC, e¹_g) by utilizing the secondary coordination sphere effect of adjacent NC–N moieties. The presence of NC–N configurations with high electronegativity modifies the degree of hybridization between Fe 3d_z², 3d_xz (3d_yz), and oxygen-containing intermediate π* orbitals, leading to an ideal balance between O₂ activation and *OH desorption. More impressively, we found that the catalysts with e_g = 1 in their metal centres may show very different activity, and the magnetic moment of 3d_xz + 3d_yz as a descriptor can accurately predict the ORR activity. Benefiting from the regulated coordination and electronic structures, the designed Fe_SAC–NC catalyst exhibited 3-fold mass activity and 7-fold specific activity than Pt/C.

中文翻译：

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操纵自旋态以激活原子分散的 Fe-N-C 催化剂以进行氧还原

^{e 为1} _g的原子分散金属-氮碳 (M-N-C) 催化剂被认为对氧还原反应非常活跃；然而，自旋状态操纵的活动起源尚不清楚。在这里，使用 Fe–N–C 作为模型催化剂，我们开发了一种简便的方法，通过利用二级配位球将其自旋状态从低自旋状态控制到中自旋状态（Fe SAC –NC，_e 1 ^g _）相邻 N C–N 部分的作用。具有高电负性的 N C–N 构型的存在改变了 Fe 3d _{z ²} , 3d _xz (3d _yz), 和含氧的中间 π* 轨道，导致 O ₂活化和 *OH 解吸之间的理想平衡。_{更令人印象深刻的是，我们发现其金属中心的 e g} = 1的催化剂可能表现出非常不同的活性，并且 3d _xz + 3d _yz的磁矩作为描述符可以准确预测 ORR 活性。得益于规范的配位和电子结构，设计的 Fe _SAC -NC 催化剂表现出比 Pt/C 高 3 倍的质量活性和 7 倍的比活性。