Curvature Strain-Induced Electron Spin Leveraging in d Orbitals toward Oxygen Reduction for Zn–Air Batteries
Linfeng Li, Yuxiao Liu, Xia Zhang, Muhammad Humayun, Haowei Yang, Jianrong Zeng, Hussein A. Younus, Yuanjie Pang, Deli Wang, Rony Snyders, Chundong Wang
Abstract
High Resolution Image Download MS PowerPoint Slide Iron phthalocyanine (FePc), with its well-defined FeN 4 active site, has attracted significant interest as a promising nonprecious catalyst in the oxygen reduction reaction (ORR). However, its rigid square-planar geometry hinders O═O bond activation and cleavage of the O═O bond, resulting in sluggish ORR kinetics. Herein, we introduce nitrogen-doped, defect-rich carbon nano-onions (CNO) (with positive Gaussian curvature) as a support to induce geometric distortion in FePc for enhancing the ORR activity. Magnetic measurements and theoretical calculations reveal that the introduction of CNO effectively promotes a spin state transition of Fe ions from low-spin (LS, t 2g 6 e g 0 ) to intermediate-spin (IS, t 2g 5 e g 1 ), which enables electron filling of the π* orbitals (via d–p orbital coupling), subsequently weakening the overadsorption of oxygenated intermediates on the FeN 4 sites. The as-fabricated FePc/CNO electrocatalyst exhibits exceptional ORR performance in alkaline media. Furthermore, a configured FePc/CNO-based Zn–air battery exhibits excellent performance, as well, demonstrating its potential for practical energy applications.