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 O 2 disengagement through its porous superaerophobic architecture. In an industrial 600 W-scale alkaline electrolyzer (679 cm 2 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 H 2 and a competitively low projected hydrogen production cost of US$ 2.38 kg H2 –1 .