Altering Ligand Fields in Single-Atom Sites through Second-Shell Anion Modulation Boosts the Oxygen Reduction Reaction
Altering Ligand Fields in Single-Atom Sites through Second-Shell Anion Modulation Boosts the Oxygen Reduction Reaction
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DOI：
10.1021/jacs.1c11331
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发表时间：
2022-02-09
影响因子：
15
通讯作者：
Xin, Huolin L.
中科院分区：
文献类型：
--
作者：
Qin, Jiayi;Liu, Hui;Xin, Huolin L.
基于金属-N-4 部分并固定在碳载体（定义为 M-N-C）上的单原子催化剂有望用于氧还原反应（ORR）。其中，具有 4d 和 5d 过渡金属 (TM4d,5d) 中心的 M-N-C 催化剂更加耐用，并且不易发生不良芬顿反应，特别是与 3d 过渡金属基催化剂相比。然而，这些TM4d,5d-N-C催化剂的ORR活性仍远不能令人满意；迄今为止，关于如何精确调节单原子TM4d、5d位点的配体场以提高其催化性能的讨论还很少。在此，我们利用单原子 Ru-N-C 作为模型系统，并报告了一种 S-阴离子配位策略来调节催化剂的结构和 ORR 性能。 S 阴离子被确定与 Ru 中心第二配位壳中的 N 原子键合，这使我们能够操纵中心 Ru 位点的电子构型。 S-阴离子配位Ru-N-C催化剂不仅具有良好的ORR活性，而且具有出色的长期耐久性，优于商业Pt/C和大多数近期单原子催化剂。 DFT 计算表明，高 ORR 活性归因于 Ru 位点 ORR 中间体的较低吸附能。在阴极侧使用这种催化剂的金属-空气电池还表现出快速的动力学和优异的稳定性。
Single-atom catalysts based on metal-N-4 moieties and anchored on carbon supports (defined as M-N-C) are promising for oxygen reduction reaction (ORR). Among those, M-N-C catalysts with 4d and 5d transition metal (TM4d,5d) centers are much more durable and not susceptible to the undesirable Fenton reaction, especially compared with 3d transition metal based ones. However, the ORR activity of these TM4d,5d-N-C catalysts is still far from satisfactory; thus far, there are few discussions about how to accurately tune the ligand fields of single-atom TM4d,5d sites in order to improve their catalytic properties. Herein, we leverage single-atom Ru-N-C as a model system and report an S-anion coordination strategy to modulate the catalyst's structure and ORR performance. The S anions are identified to bond with N atoms in the second coordination shell of Ru centers, which allows us to manipulate the electronic configuration of central Ru sites. The S-anion-coordinated Ru-N-C catalyst delivers not only promising ORR activity but also outstanding long-term durability, superior to those of commercial Pt/C and most of the near-term single-atom catalysts. DFT calculations reveal that the high ORR activity is attributed to the lower adsorption energy of ORR intermediates at Ru sites. Metal-air batteries using this catalyst in the cathode side also exhibit fast kinetics and excellent stability.