Lewis Acid‐Base Molecular Anchoring Through Oxygen Vacancies Enables Ultrastable and High‐Conductivity Membranes for Alkaline Water Electrolysis

ABSTRACT The performance of alkaline water electrolysis for green hydrogen production is critically dependent on membrane, which is often constrained by a trade‐off between ionic conductivity and gas impermeability. Here, this challenge is overcome through a universal defect engineering strategy centered on metal oxide nanoparticles. By creating a high density of oxygen vacancies in zirconia (ZrO 2 ), we transform the nanoparticles into potent Lewis acid sites. This dual functionality engineers the polymer‐filler interface to create continuous, low‐resistance pathways for rapid OH − transport, while simultaneously establishing strong Lewis acid‐base “molecular anchoring” to the polymer matrix and support mesh. This robust interfacial cohesion yields a thin composite membrane (≈190 µm) with an ultralow area resistance (0.08 Ω cm 2 ) and a remarkable bubble point pressure (5.6 bar). Consequently, an AWE cell achieves an relevant current density of 2 A cm −2 at only 1.82 V and demonstrates exceptional durability over 730 h. This vacancy‐mediated interfacial engineering paradigm, proven effective for TiO 2 and CeO 2 as well, offers a powerful and broadly applicable strategy for developing advanced membranes for electrochemical energy systems.