Building Cobalt-Nickel Diatomic Sites as Oxygenophilic ORR Catalyst with Strong Cl−-Corrosion Resistance for Seawater Batteries

The seawater battery (SWB) holds great potential as the next-generation energy supply system for marine electrical equipment. However, its efficiency and durability are hindered by low oxygen concentration and harmful Cl⁻ adsorption and corrosion in seawater. Herein, a host-guest strategy is developed to fabricate diatomic catalysts with adjacent Co and Ni sites on nitrogen-doped carbon (CoNi-DAC), where Co and Ni atoms are each coordinated to three nitrogen atoms. Theoretical calculations and in situ characterization reveal that the synchronized reduction of Co and Ni valence states enhances ORR kinetics by optimizing the O₂ adsorption energy barrier, facilitating direct O─O bond cleavage and preventing *OOH intermediate formation. This electronic modulation enhances oxygenophilicity and Cl⁻ corrosion resistance. The Co/Ni diatomic sites synergistically improve ORR catalytic activity, achieving a half-wave potential (E_1/2) of 0.79 V and exceptional long-term durability of nearly 700 h in natural seawater. The assembled SWB with CoNi-DAC coated carbon brush electrode attains a peak power density of 3.3 W L⁻¹. This work offers valuable insights into the design and development of advanced ORR electrocatalysts for natural seawater environments.