Single-atomic iron synergistic atom-cluster induce remote enhancement toward oxygen reduction reaction

The oxygen reduction reaction (ORR) could be effectively regulated by adjusting electron configurations and optimizing chemical bonds. Herein, we have achieved the modulation of electron distribution in Fe single atomic (Fe_SA) sites through Fe atomic clusters (Fe_AC) via a confined pyrolysis approach, thereby enhancing their intrinsic ORR activity. X-ray absorption spectroscopy has confirmed that the presence of iron atomic clusters could influence the electron distribution at Fe-N₄ sites. The Fe_SA/Fe_AC-NC catalyst exhibits a half-wave potential of 0.88 V, surpassing the individual Fe_SA-NC structure. Through electronic structure analysis, it could be seen that iron atom clusters can affect Fe-N₄ sites through long-range effects, and then effectively lower reaction barriers and enhance the reaction kinetics at Fe-N₄ sites. The synthetic approach might pave the way for constructing highly active catalysts with tunable atomic structures, representing an effective and universal technique for electron modulation in M-N-C systems. This work provides enlightenment for the exploration of more efficient single-atom electrocatalysts and the optimization of the performance of atomic electrocatalysts. Furthermore, a zinc-air battery assembled using it on their cathode deliver a high peak power density (205.7 mW cm⁻²) and a high-specific capacity of 807.5 mA h g⁻¹. This study offers a fresh approach to effectively enhance the synergistic interaction of between Fe single atom and Fe atomic clusters for improving ORR activity and energy storage.