Suppression of chlorine-related side reactions via spin control for sustainable seawater electrolysis

Seawater electrolysis offers a promising route to green hydrogen production by utilizing abundant seawater resources, yet its commercial viability is hindered by chlorine-related side reactions that cause corrosion and reduce efficiency. Current strategies mainly employing anion-enriched layers to repel chloride ions face challenges, as these pre-designed structures may not dynamically maintain selective exclusion under varying operational potentials. Here, we propose a fundamentally different approach based on spin-mediated selectivity and employ a series of spinel oxides with varying magnetic properties to elucidate the correlation between spin regulation, anodic reaction selectivity, and electrolysis stability. We demonstrate that ferromagnetic catalysts intrinsically strengthen hydroxyl adsorption while suppressing chloride binding, thereby favoring oxygen evolution over competing chlorine chemistry. Mechanistically, spin alignment facilitates the formation of triplet oxygen and inhibits chlorinated byproducts. Benefiting from such intrinsic selectivity, catalysts with stronger ferromagnetism exhibit superior operational stability in seawater electrolysis, maintaining stable performance for 120 h in an anion exchange membrane water electrolyzer. This work establishes spin regulation as a complementary strategy for designing highly selective and durable electrocatalysts, offering a new pathway to address the limitations of conventional protection layers in practical seawater splitting.