Engineering Controllable Coordination Shells of Axial Single Atoms for Tuning Oxygen Reduction Reaction in Alkaline Seawater Electrolytes

ABSTRACT Seawater aluminum‐air batteries (S‐AABs) are considered a promising solution for the efficient generation of marine power due to their low cost, high energy density, and the abundance of seawater resources. However, the oxygen reduction reaction (ORR) at the cathode in seawater electrolytes is severely hindered by Cl − interference, which drastically degrades the efficiency and stability. This work establishes a synergistic optimization system that combines a controllable coordination shell environment with an axial coordination protective layer to construct highly efficient ORR catalysts resistant to Cl − corrosion. Specifically, precise control over S coordination (first/second shell) in axially coordinated Fe‐N 5 catalysts is achieved by regulating atomic doping sequence. In situ characterizations and density functional theory calculations reveal that second‐shell S induces more prominent axial‐shell synergistic effects: S optimizes the electronic structure and bonding strength of Fe active sites, and more critically, drives remote charge transfer from Fe to axial N, forming a robust negative charge barrier against Cl − . Accordingly, the S‐AABs exhibit a high peak power density of 220.80 mW·cm −2 and a remarkable lifespan surpassing 120 h. This work paves a generalizable pathway for the design of highly active and stable electrocatalysts suitable for advanced and long‐lived seawater‐based energy storage devices.