NiN 4 C‐Coordination Stabilized Cobalt‐Based Single Cluster Catalyst with High Active Site Density: Rationally Designed Atomic Architecture Boosts Oxygen Reduction Activity

ABSTRACT The rational design of single‐cluster catalysts (SCCs) for the oxygen reduction reaction (ORR) is hindered by difficulties in achieving atomic precision, high site‐density and resistance to aggregation during synthesis and operation. To address these challenges, we report a NiN 4 C‐coordinated cobalt‐based SCC which is synthesized via a gradient pyrolysis‐driven stepwise anchoring strategy that enables the sequential thermal anchoring of Ni and Co species. Well‐defined NiN 4 C moieties are anchored on the carbon support at the lower pyrolysis temperature; these sites subsequently capture cobalt oxide fragments at a higher pyrolysis temperature, leading to the formation of a NiN 4 C‐site coordinated stable Co 3 O 5 NiN 4 C ensemble. Advanced in situ spectroscopy, cyclic voltammetry and density functional theory calculations infer its electrochemical transformation into an active Co 3 O 1 NiN 4 C phase prior to the onset of ORR. The triangular Co 3 motif facilitates side‐on adsorption, elongating the O‐O bond and lowering the dissociation energy barrier for the rate‐determining step. Consequently, the catalyst delivers exceptional ORR performance, achieving a half‐wave potential of 0.923 V vs. RHE, an active‐site density of 4.16 × 10 20 sites g −1 , and a peak power density of 247.3 mW cm −2 in Zinc‐air batteries. This work provides an effective strategy for designing stable, efficient oxygen electrocatalysts by precisely engineered cluster architecture.