Osmium Nanoparticle Anchoring on CoFe Layered Double Hydroxides Enables High-Valent Species Stabilization and Efficient Seawater Oxygen Evolution.

Direct seawater oxygen evolution reaction (OER) is critically hampered by chloride-induced competitive oxidation, corrosion, and active-site poisoning, driving the urgent need for highly active and chlorine-tolerant electrocatalysts. Herein, a surface-engineered electrocatalyst comprising osmium nanoparticles (Os NPs) anchored onto CoFe layered double hydroxide (Os/CoFe LDH) was prepared. X-ray photoelectron spectroscopy revealed that the incorporated Os NPs stabilized high-valence Co/Fe species, which preferentially promote OH- adsorption over Cl- and function as the genuine active centers for OER. Furthermore, in situ Raman spectroscopy demonstrates that Os NPs anchoring modulates the interfacial water structure, thereby enhancing water adsorption and facilitating seawater OER kinetics. The optimized Os/CoFe LDH-40 achieves an overpotential of only 244 mV at 10 mA cm-2 in simulated alkaline seawater and operates stably for over 300 h in an anion exchange membrane electrolyzer at 300 mA cm-2. This work not only develops a high-performance catalyst for alkaline seawater OER but also offers new perspectives for advancing osmium-based materials in electrocatalysis.