Enhancing Oxygen Reduction Reaction Performance Through Abundant Single Fe Atoms for Advanced Zinc–Air Batteries

Iron- and nitrogen-codoped carbon (Fe–N–C) catalysts with Fe–N₄ active sites offer a promising alternative to noble metal-based materials for the oxygen reduction reaction (ORR), which is essential for energy storage and conversion in applications such as fuel cells and metal–air batteries. This study presents a straightforward and scalable method to synthesize an efficient ORR electrocatalyst that consists of nitrogen-doped carbon and a high density of atomically dispersed single iron atoms, created through the pyrolysis of Fe-zeolitic imidazolate framework (Fe-ZIF-8) precursors. The Fe-ZIF-8 framework effectively restricts the migration and agglomeration of iron species, resulting in obtained Fe–N–C with conductive, mesoporous carbon structures and abundant Fe–N₄ sites. This structure provides excellent electrocatalytic activity for the ORR, demonstrated by a positive onset potential of 0.985 V vs RHE and a half-wave potential of 0.905 V vs the reversible hydrogen electrode (RHE) in alkaline media, outperforming commercial Pt/C. Additionally, when used as the cathode in a zinc–air battery, the Fe–N–C catalyst delivers high maximum power densities of 170.1 mW cm^–2, showcasing its potential for practical energy storage applications.