Asymmetric tacticity navigates the localized metal spin state for sustainable alkaline/sea water oxidation

Anodic oxygen evolution reaction (OER) that involves a spin-dependent singlet-to-triplet oxygen changeover largely restrains the water electrolysis efficiency for hydrogen production. However, the modulation of spin state is still challengeable for most OER catalysts, and there remains a debate on deciphering the active spin state in OER. Here, we pioneered an asymmetric Fe-incorporated NiPS₃ tactic system to retune the metal localized spin for efficient OER electrocatalysis. It is unraveled that the synergistic effect of medium-spin Fe^III site and P/S coordination can effectively boost OER activity and Cl resistance selectivity in alkaline/sea water. Resultantly, the Fe/NiPS₃-based asymmetric electrodes exhibit low cell voltages of 1.50 volts/1.52 volts in alkaline/sea water at 10 milliamperes per square centimeter, together with a sustainable retention for 1000 hours. It also delivers the durable performance in anion exchange membrane water electrolyzers with a low operation voltage at 45°C. This research navigates the atomic localized spin state as the criterion in rationalizing efficient nonprecious alkaline/sea water oxidation electrocatalysts.