Asymmetric Fe-N3Se single atoms coupled with Fe atomic clusters on alveolar-inspired hierarchically porous carbon submicronspheres for enhanced oxygen reduction

Conventional metal-nitrogen-carbon single-atom catalysts (M-N-C SACs) are plagued by electron localization effects arising from symmetric coordination geometries and the absence of synergistic interactions among isolated active sites, both of which critically undermine oxygen reduction reaction (ORR) catalytic performance. To address these limitations, this study introduces a multiscale synergistic engineering strategy that integrates asymmetric coordination design with bioinspired structural innovation. Specifically, the symmetry of the Fe-N 4 coordination is disrupted to generate Fe-N 3 Se sites, which facilitate charge density redistribution; while Fe atomic clusters (FeACs) are strategically integrated to construct asymmetric catalytic centers that activate O 2 and promote O-O bond cleavage. A hierarchical porous carbon submicronspheres architecture, inspired by alveolar structures and featuring gradient-distributed micropores and mesopores, has been developed to enhance the mass transport efficiency at triple-phase interface. Overall, we have developed FeSAs and FeACs anchored on alveolar-inspired hierarchically porous nitrogen/selenium co-doped carbon submicronspheres (Fe SA+AC -N/Se-AHCs), which exhibits outstanding ORR activity (E o =0.99 V, E 1/2 =0.90 V) and long-term durability. Theoretical analyses further demonstrate that the electronic coupling between Fe-N 3 Se sites and FeAC synergistically optimizes the adsorption free energies of critical *OOH and *O intermediates, thereby accelerating O-O bond dissociation. This work presents a comprehensive cathode catalyst platform for developing high-energy-density and long-cycle-life Zinc-air batteries.