Magnetic Moment Descriptor‐Guided Multifunctional Co Single‐Atom Catalysts Enable Wide‐Temperature Uninterrupted Seawater Splitting

Abstract Developing chloride ion‐resistant trifunctional catalysts is imperative and of great significance for application in renewable energy‐driven seawater splitting systems (S‐WSS). However, there is currently a lack of unified descriptors for the rational design of catalysts that possess both high corrosion resistance and excellent catalytic activity. Herein, the magnetic moment is proposed as the descriptor through second‐coordination‐shell anion engineering of CoN₄ moieties (named as CoN 4 ‐X, X = B/O/F/P/S/Cl). Systematic density functional theory calculations reveal that precisely modulating the spin states of CoN₄ centers via X‐anion coordination establishes dual volcano‐type relationships between magnetic moments and the adsorption energetics of Cl⁻ ions or key reaction intermediates for oxygen reduction, oxygen evolution, and hydrogen evolution reactions (ORR/OER/HER). Experimental validation demonstrates the optimized CoN₄‐B configuration‐based catalyst (Co SAs‐N/B‐HCS) achieves minimized Cl⁻ adsorption energy while delivering exceptional trifunctional ORR/OER/HER activity, as well as excellent stability in chloride ion‐rich seawater‐based environments (over 1000 h for seawater‐based Zn‐air batteries, over 800 h for seawater splitting). Notably, the Co SAs‐N/B‐HCS enables temperature‐adaptive hydrogen production rates of 853 µmol h⁻¹ (60 °C), 616 µmol h⁻¹ (25 °C), and 397 µmol h⁻¹ (−30 °C). This work establishes a spin state engineering paradigm that simultaneously addresses catalyst corrosion and trifunctional synergy in marine energy systems.