Precisely Engineering Asymmetric Atomic CoN4 by Electron Donating and Extracting for Oxygen Reduction Reaction

• Published in: Angewandte Chemie International Edition Vol. 63; no. 21; pp. e202315802 - n/a
• Main Authors: Lv, Minghui, Cui, Cheng‐Xing, Huang, Niu, Wu, Mingzhu, Wang, Qiao, Gao, Tao, Zheng, Yong, Li, Hui, Liu, Wei, Huang, Yingping, Ma, Tianyi, Ye, Liqun
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 21.05.2024
• Edition: International ed. in English
• Subjects: Catalysts; Catalytic activity; Chelation; Chemical reduction; Cobalt; Coordination; Electrocatalysts; Electron density; electron-donating or electron-withdrawing properties; Ligands; nonpyrolytic catalysts; ORR catalytic activity; Oxygen reduction reactions; Triazine; well-defined CoN4 centers; nonpyrolytic catalysts; well-defined CoN4 centers; electron density; electron-donating or electron-withdrawing properties; ORR catalytic activity
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.202315802

The development of nonpyrolytic catalysts featuring precisely defined active sites represents an effective strategy for investigating the fundamental relationship between the catalytic activity of oxygen reduction reaction (ORR) catalysts and their local coordination environments. In this study, we have synthesized a series of model electrocatalysts with well‐defined CoN4 centers and nonplanar symmetric coordination structures. These catalysts were prepared by a sequential process involving the chelation of cobalt salts and 1,10‐phenanthroline‐based ligands with various substituent groups (phen(X), where X=OH, CH3, H, Br, Cl) onto covalent triazine frameworks (CTFs). By modulating the electron‐donating or electron‐withdrawing properties of the substituent groups on the phen‐based ligands, the electron density surrounding the CoN4 centers was effectively controlled. Our results demonstrated a direct correlation between the catalytic activity of the CoN4 centers and the electron‐donating ability of the substituent group on the phenanthroline ligands. Notably, the catalyst denoted as BCTF−Co‐phen(OH), featuring the electron‐donating OH group, exhibited the highest ORR catalytic activity. This custom‐crafted catalyst achieved a remarkable half‐wave potential of up to 0.80 V vs. RHE and an impressive turnover frequency (TOF) value of 47.4×10−3 Hz at 0.80 V vs. RHE in an alkaline environment. By coordinating cobalt salts and 1,10‐phenanthroline ligands with different substituents (phen(X), X=OH, CH3, H, Br, Cl) onto CTFs, a series of well‐defined CoN4 centers were synthesized as model electrocatalysts. The experimental results proved a positive correlation between the electron‐pushing ability of the substituent groups on the phen‐based ligands and both the adsorption strength of the CoN4 centers on oxygen molecules and their ORR kinetic activity.