Large-scale synthesis of N-doped carbon capsules supporting atomically dispersed iron for efficient oxygen reduction reaction electrocatalysis

• Published in: eScience (Beijing) 2022-03, Vol.2 (2), p.227-234
• Main Authors: Yang, Hui, Liu, Yanfang, Liu, Xiaolu, Wang, Xiangke, Tian, He, Waterhouse, Geoffrey I.N., Kruger, Paul E., Telfer, Shane G., Ma, Shengqian
• Format: Article
• Language: English
• Subjects: Electrocatalysis; Hollow carbon capsules; Metal single atoms; Metal–organic framework; Oxygen reduction reaction
• ISSN: 2667-1417; 2667-1417
• DOI: 10.1016/j.esci.2022.02.005

The large-scale synthesis of platinum-free electrocatalysts for the oxygen reduction reaction (ORR) remains a grand challenge. We report the large-scale production of stable and active ORR electrocatalysts based on iron, an earth-abundant element. A core–shell zeolitic imidazolate framework–tannic acid coordination polymer composite (ZIF-8@K-TA) was utilized as the catalyst precursor, which was transformed into iron atoms dispersed in hollow porous nitrogen-doped carbon capsules (H-Fe-Nx-C) through ion exchange and pyrolysis. H-Fe-Nx-C features site-isolated single-atom iron centers coordinated to nitrogen in graphitic layers, high levels of nitrogen doping, and high permeability to incoming gases. Benefiting from these characteristics, H-Fe-Nx-C demonstrated efficient electrocatalytic activity (E1/2 ​= ​0.92 ​V, vs. RHE) and stability towards the ORR in both alkaline and acidic media. In ORR performance, it surpassed the majority of recently reported Fe-N-C catalysts and the standard Pt/C catalyst. In addition, H-Fe-Nx-C showed outstanding tolerance to methanol. A rationally designed MOF-based composite was employed as a precursor for the large-scale synthesis of hollow porous nitrogen-doped carbon capsules containing well-dispersed metal single-atom sites (H-Fe-Nx-C). This architecture gave H-Fe-Nx-C outstanding ORR activity and good methanol tolerance. [Display omitted] •A hollow Fe-Nx-C was synthesized through ion exchange and pyrolysis.•H-Fe-Nx-C could be synthesized on a large scale if required.•H-Fe-Nx-C showed efficient electrocatalytic activity towards the ORR.