Polymeric Hydrogel Interphase Enables Transport-Compatible Fe Stabilization for Hectowatt-Scale Alkaline Water Electrolysis.

Achieving durable oxygen evolution reaction (OER) under industrial alkaline water electrolysis (AWE) conditions remains a formidable challenge, arising from dynamic Fe dissolution and segregation in NiFe layered double hydroxides (LDH) and further aggravated by sluggish ion transport and bubble release at the gas-liquid-solid interface. Herein, we report a design concept of using an ultrathin sodium polyacrylate (PANa) hydrogel layer on NiFe LDH as a spatially confining, transport-permissive interphase to dynamically stabilize Fe sites and enhance multiphase interfacial transport for boosting OER durability in hectowatt-scale AWE. We demonstrate that the PANa interphase converts uncontrolled Fe dissolution-segregation into an interfacially confined and self-regulated dissolution-redeposition process, in which carboxylate-mediated Fe-O-C coordination thermodynamically stabilizes lattice Fe by suppressing overoxidation, while the hydrated polymer network kinetically retains transiently dissolved Fe within the interfacial region and favors its reincorporation toward homogeneous active-phase regeneration. Meanwhile, the carboxylate-rich framework reorganizes the interfacial hydrogen-bond network to accelerate OH- transport and promote rapid O2 disengagement through its porous superaerophobic architecture. In an industrial 600 W-scale alkaline electrolyzer (679 cm2 total anode area), the PANa/NiFe LDH anode sustains stable operation for over 2500 h at 0.5 A cm-2, with an energy consumption as low as 4.25 kWh Nm-3 H2 and a competitively low projected hydrogen production cost of US$ 2.38 kgH2-1.