The coordination engineering of Fe–N–C single-atom catalysts (SACs) through introducing heteroatom dopants has attracted widespread attention in the oxygen reduction reaction (ORR). However, the common regularity for tuning the ORR activity by coordinated and environmental heteroatoms has not been sufficiently studied. Herein, we study the ORR activity on 100 Fe–N–C SACs with S, P, and B heteroatoms in diverse coordination shells by density functional theory calculations. Based on the energy level distribution of frontier orbits and molecular orbital theory, it is found that the origin of Fe–N–C ORR activity is the hybridization of molecular orbitals of Fe 3d_z2, 3d_yz (3d_xz), and O₂*/OH* intermediates, where hybrid orbitals are adjusted by coordinated and environmental S, P, and B heteroatoms, and then the protonation process of O₂* or OH* intermediate is determined. Moreover, we found that the Fe–O bond length, the d-orbital gap of spin states, the d-orbital center, and the valence state of the Fe site can be used as structural descriptors to predict the ORR activity governed by the protonation of O₂* or OH* intermediate as potential-determining steps. Our structural descriptors rationalize the superior ORR performance of Fe–N–C with S or B atoms doped in the second coordination shell to those in the first coordination shell, as well as the fact that the P heteroatom is more suitable as a coordinated atom than the environmental atom to enhance the ORR activity of Fe–N–C, in available experimental references. Thanks to structural descriptors, the codoping synergistic effect between P in the first coordination shell and S in the second coordination shell is predicted and confirmed to greatly enhance the ORR activity. This study provides a unified mechanistic understanding on the ORR activity trend among Fe–N–C SACs regulated by coordinated and environmental heteroatoms.

中文翻译：

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通过简单描述符合理设计用于氧还原反应的杂原子掺杂 Fe-N-C 单原子催化剂

通过引入杂原子掺杂剂的Fe-N-C单原子催化剂（SAC）的配位工程在氧还原反应（ORR）中引起了广泛的关注。然而，通过配位和环境杂原子调节 ORR 活性的常见规律尚未得到充分研究。在此，我们通过密度泛函理论计算研究了 100 个具有 S、P 和 B 杂原子的不同配位壳层的 Fe-N-C SAC 的 ORR 活性。基于前沿轨道能级分布和分子轨道理论，发现Fe-N-C ORR活性的根源是Fe 3d _{z 2}、3d _yz (3d _xz )和O ₂分子轨道的杂化*/OH*中间体，通过配位和环境S、P、B杂原子调整杂化轨道，然后确定O ₂ * 或OH*中间体的质子化过程。此外，我们发现Fe-O键长、自旋态的d轨道间隙、d轨道中心和Fe位点的价态可以作为结构描述符来预测由质子化控制的ORR活性O ₂ * 或OH * 中间体作为电位确定步骤。我们的结构描述符合理化了第二配位壳中掺杂有 S 或 B 原子的 Fe-N-C 比第一配位壳中掺杂的 Fe-N-C 优越的 ORR 性能，以及 P 杂原子比杂原子更适合作为配位原子这一事实环境原子增强 Fe-N-C 的 ORR 活性，在现有的实验参考文献中。借助结构描述符，预测并证实了第一配位层中的 P 和第二配位层中的 S 之间的共掺杂协同效应，从而大大增强了 ORR 活性。这项研究为 Fe-N-C SAC 受协调和环境杂原子调节的 ORR 活性趋势提供了统一的机制理解。