Engineering an iron atom-cluster nanostructure towards efficient and durable electrocatalysis

Iron-based catalysts have demonstrated fascinating activities in the oxygen reduction reaction (ORR), especially due to the synergistic effect between atoms and clusters, but challenging for further improvement. Herein, a strategy is developed to optimize the catalyst with nitrogen-coordinated Fe single atoms (SAs) and closely surrounding Fe atomic clusters (ACs) towards efficient ORR. The FeSA/FeAC-NC 900 delivers excellent ORR activity with half-wave potential (E1/2) in both acidic (0.80 V) and alkaline (0.90 V) media, as well as superior stability. Theoretical calculations further reveal that the synergistic effects of Fe-based SAs and ACs along with porous structures can decrease the overall energy barrier in the ORR process. Besides, the FeSA/FeAC-NC 900-based zinc–air battery manifests a high peak power density (214.3 mW cm−2) and a high-specific capacity (773.6 mA h g−1). This work provides a new perspective to highly optimize the synergistic interaction of SAs and ACs for boosting activity and energy storage.