Redefining catalyst reconstruction and Cl--repulsion correlation to delineate a dynamic protective skeleton for seawater splitting

From the perspective of sustainable energy and green hydrogen, the critical challenge in seawater electrolysis lies in suppressing competitive chloride oxidation and corrosion at the anode. Despite the proposed protection mechanism based on surface reconstruction-derived anion repellence, a fundamental question of selectivity remains: why does the protective layer exclude Cl- but not the formally equivalent OH-? We now redefine the connection between reconstruction and interfacial protection in NiFeS anodes to elucidate the origin of underlying selectivity. In-situ Raman, in-situ X-ray absorption spectroscopy, and molecular dynamic calculations further confirm that the reconstructed SO42- establishes an enhanced hydrogen-bond network. This network significantly weakens the hydrogen-bonding strength of Cl- relative to H2O, thereby enhancing the discrimination between OH- and Cl-. In practical application, NiFeS demonstrates energy-saving seawater splitting performance (261.8 mV @ 100 mA·cm-2), long-term durability (2000 h @ 1.0 A·cm-2), and enables stable intermittent electrolysis (1500 start-stop cycles @500 mA·cm-2). When integrated into an anion exchange membrane cell, it shows promising electrolysis performance for industrial applications (1.970 V @ 1.0 A·cm-2). Seawater electrolysis for green hydrogen faces the critical challenge of preventing chloride oxidation. Here, the authors report that reconstructed sulfate layers on NiFeS anodes establish a hydrogen-bond network that selectively weakens chloride binding while allowing hydroxide access for electrolysis.