Cobalt Single-Atom Electrocatalysts Enhanced by Hydrogen-Bonded Organic Frameworks for Long-Lasting Zinc-Iodine Batteries

Herein, a hydrogen-bonded cobalt porphyrin framework is presented that can efficiently host iodine and serve as an electrocatalyst for aqueous zinc-iodine (Zn-I-2) organic batteries. The Fourier Transform infrared spectroscopy (FT-IR), X-ray Photoelectron Spectroscopy (XPS), and Density functional theory (DFT) results demonstrate that hydrogen-bonded organic frameworks (HOFs) possess excellent adsorption properties for iodine species. In situ Raman spectroscopy illustrates that the redox mechanism of Zn-I-2 battery depends on the redox reaction of I/I-, with I-3(-)/I-5(-) serving as intermediary products. The in situ Ultraviolet-visible (UV-vis) spectroscopy further reveals that HOFs restrict polyiodide solubilization. The aqueous Zn-I-2 organic batteries with I-2@PFC-72-Co cathodes exhibit excellent rate capability, achieving 134.9 mAh g(-1) at 20 C. Additionally, these batteries demonstrate long-term cycle stability, enduring > 5000 cycles at 20 C. The impressive electrochemical performance of I-2@PFC-72-Co can be attributed to the cooperative Co single-atom (CoSA) electrocatalyst in the HOF-Co structure. Moreover, the benzene ring structure and the carboxyl functional group of HOFs possess a strong ability to adsorb iodine and iodide. Owing to these synergistic effects, the aqueous Zn-I-2 batteries with the I-2@PFC-72-Co cathode exhibit excellent electrochemical performance.