Curvature Strain-Induced Electron Spin Leveraging in d Orbitals toward Oxygen Reduction for Zn-Air Batteries.
basic_science · Level V
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- Record sourced from PubMed, PMID 41193250.
- Also identified by DOI 10.1021/acs.nanolett.5c04405.
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Abstract
Iron phthalocyanine (FePc), with its well-defined FeN<sub>4</sub> 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<sub>2g</sub><sup>6</sup> e<sub>g</sub><sup>0</sup>) to intermediate-spin (IS, t<sub>2g</sub><sup>5</sup> e<sub>g</sub><sup>1</sup>), which enables electron filling of the π* orbitals (via d-p orbital coupling), subsequently weakening the overadsorption of oxygenated intermediates on the FeN<sub>4</sub> 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.