B-Site engineered bilayered Ruddlesden-Popper ferrites for efficient oxygen evolution and overall water electrolysis

Developing durable oxygen evolution reaction (OER) electrocatalysts is pivotal for hydrogen production but hindered by sluggish kinetics. While Ruddlesden-Popper (RP) oxides offer a versatile platform, they often suffer from limited active site density. Herein, we present a targeted B-site engineering strategy to activate bilayer RP ferrites (La 0.25 Sr 2.75 Fe 2 O 7 ) via systematic Ni incorporation. This substitution strengthens B-O covalency and enriches oxygen vacancies. The optimized LSFN50 exhibits a low overpotential of 344 mV at 10 mA cm -2 , surpassing commercial IrO 2 . Mechanistic studies indicate a pH-dependent pathway. Systematic structural and chemical analyses reveal that high-valence Ni 3+ and Fe-Ni synergy drive surface reconstruction into active oxyhydroxides, with lattice oxygen participation further boosting reaction kinetics. Significantly, an anion exchange membrane (AEM) water electrolyzer employing the LSFN50 anode delivers an industrial-grade current density of 2.23 A cm -2 at 1.9 V. This study highlights the critical role of B-site modulation in designing high-performance catalysts for practical energy conversion.