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

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 1/4 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.

Automated summary

The large-scale production of stable and active ORR electrocatalysts based on iron was achieved using a core-shell zeolitic imidazolate framework-tannic acid coordination polymer composite (ZIF-8@K-TA) as the catalyst precursor. The resulting H-Fe-Nx-C demonstrated efficient electrocatalytic activity and stability towards the ORR, surpassing the majority of recently reported Fe-N-C catalysts and the standard Pt/C catalyst, with outstanding tolerance to methanol.