Qin Jiayi, Liu Hui, Zou Peichao, Zhang Rui, Wang Chunyang, Xin Huolin L
Department of Physics and Astronomy, University of California, Irvine, California 92697, United States.
J Am Chem Soc. 2022 Feb 9;144(5):2197-2207. doi: 10.1021/jacs.1c11331. Epub 2022 Jan 28.
Single-atom catalysts based on metal-N 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 (TM) 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 TM-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 TM 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.
基于金属 - N部分并锚定在碳载体上的单原子催化剂（定义为M - N - C）在氧还原反应（ORR）方面具有潜力。其中，具有4d和5d过渡金属（TM）中心的M - N - C催化剂更耐用，不易发生不良的芬顿反应，特别是与基于3d过渡金属的催化剂相比。然而，这些TM - N - C催化剂的ORR活性仍远不能令人满意；到目前为止，关于如何精确调节单原子TM位点的配体场以改善其催化性能的讨论很少。在此，我们以单原子Ru - N - C作为模型体系，报道一种S - 阴离子配位策略来调节催化剂的结构和ORR性能。已确定S阴离子与Ru中心第二配位层中的N原子键合，这使我们能够操纵中心Ru位点的电子构型。S - 阴离子配位的Ru - N - C催化剂不仅具有有前景的ORR活性，而且具有出色的长期耐久性，优于商业Pt/C和大多数近期的单原子催化剂。密度泛函理论计算表明，高ORR活性归因于ORR中间体在Ru位点的较低吸附能。在阴极侧使用这种催化剂的金属空气电池也表现出快速动力学和出色的稳定性。
