Shielding Co ₃ O ₄ by Inert Carbonized Polymer Dots Enables Chlorine Resistance Toward Durable Ampere‐Level Oxygen Evolution

ABSTRACT Seawater electrolysis is crucial for large‐scale green hydrogen production, yet high concentrations of chloride ions (Cl − ) result in competitive adsorption, leading to severe catalyst degradation and electrode corrosion. To address this challenge, we develop a Co 3 O 4 @carbonized polymer dots (CPDs) electrocatalyst, which achieves a low overpotential of 270 mV at 500 mA cm −2 , together with outstanding durability of 4200 h at 600 mA cm −2 and 3200 h at 800 mA cm −2 . An anion exchange membrane simulated‐seawater electrolyzer (AEMSE) based on Co 3 O 4 @CPDs achieves stable seawater electrolysis for over 1500 h at 1.0 A cm −2 with a very low cell voltage of 1.73 V. The combined experimental and theoretical studies reveal that CPDs stabilize the lattice oxygen and decrease the reaction energy barrier, thereby switching the lattice oxygen‐mediated mechanism (LOM) pathway to more desired adsorbate evolution mechanism (AEM). Furthermore, surface‐anchored CPDs generate CO 3 2− through electro‐oxidation, forming a protection system that blocks Cl − adsorption and penetration. This strategy successfully overcomes the corrosion bottleneck in seawater electrolysis and opens new avenues for sustainable hydrogen energy development.