Defect-rich Birnessite Ultrathin Nanosheet Array Armed with Fe-Phytate Complex Enables Boosted and Long-Lasting Seawater Oxidation at Industrial-Level Current Density

Seawater electrolysis is appealing for mass production of high-purity H2, yet it remains challenging in engineering an efficient and robust oxygen evolution reaction (OER) anode to avoid undesired chloride oxidation reactions and resist chloride corrosion. Herein, we report a multilayered electrode with a Fe-phytate (Fe-PA) complex armor capped on the defect-rich Ni-doped δ-MnO2 ultrathin nanosheet array aligned on 3D macroporous Ni foam for boosted and sustained seawater oxidation at an industrial-level current density. From comprehensive experimental and theoretical investigations, the integration of the defect-rich Ni-MnO2 ultrathin nanosheet array configuration with a surface Fe-PA modification can provide abundant catalytic sites featuring an optimized electronic structure to promote the rate-determining step of *OH deprotonation to inherently boost the OER, and meanwhile impart superhydrophilicity and quasi-superaerophobicity to accelerate electrolyte infiltration and bubble detachment for facilitated mass transport. Impressively, the multilayered architecture comprising an inherently anticorrosive δ-MnO2 core and Fe-PA complex armor could cooperatively contribute to promoting corrosion resistance via effective chloride repelling. This work opens up a promising avenue for constructing MnO2-based materials toward promoted and long-lasting seawater oxidation via geometric and electronic modulation, which represents a significant step in advancing seawater electrolysis technology.