Dual Sites of Fe─N ₄ /Co─N ₄ Single Atoms and the Third Site of Pillaring FeCo Nanoparticles Synergistically Enable Exceptionally Bifunctional Activity for Oxygen Electrocatalysis

ABSTRACT Non‐precious triple‐site (tri‐site) electrocatalysts that combine bimetallic single atoms with nanoparticles are promising for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, we presentg a strategy of precisely constructing a tri‐site catalyst, FeCo _SA/NP @NGA‐600, with a low concentration of metal precursors at a relatively low pyrolysis temperature of 600°C. This catalyst comprises a relatively high density of iron single‐atom sites (Fe─N ₄ ), cobalt single‐atom sites (Co─N ₄ ), and small‐sized iron‐cobalt alloy nanoparticles (FeCo _NP ), achieving efficient synergistic catalysis. This catalyst also forms a biomimetic hierarchical pore architecture, ensuring sufficient site exposure and fast mass transport, demonstrating outstanding catalysis activity: a 0.93 V half‐wave potential for ORR, a 1.54 V overpotential for OER, and a 385 h cycle life in a liquid zinc‐air battery (LZAB), better than commercial Pt/C and RuO ₂ . With experimentally‐guided construction of tri‐site models, theoretical calculations reveal that the inherent synergy is associated with electronic modulation, optimized O ₂ adsorption, and direct O─O bond cleavage ( ^* OOH → ^* O + ^* OH) in ORR kinetically, and a low energy barrier in the rate‐determining step thermodynamically. This study contributes an effective approach to design and an insightful understanding of multi‐site masterful electrocatalysts containing metals with different coordination abilities.