Corrosion-Driven Ni₃S₄ Gradient in NiFe-LDH Enables Durable Industrial-Scale Water Electrolysis

Designing low-cost yet highly efficient oxygen evolution reaction (OER) electrocatalysts is essential to enable sustainable green hydrogen generation. However, synthesis complexity, slow kinetics, and poor durability hinder industrial use. In this study, we present a corrosion-driven gradient engineering approach for the rapid, energy-free synthesis of Ni₃S₄/NiFe-LDH heterostructures on iron foam (IF) under ambient conditions. During spontaneous IF corrosion, a compositional and gradient structure forms, with Ni₃S₄ dominating the surface and NiFe-LDH enriching the core, establishing a continuous pathway for rapid electron transport. The catalyst exhibits superior OER performance, achieving low overpotentials of 297 mV in 1 M KOH and 326 mV in simulated seawater at 500 mA cm^-2. Notably, in pure-water anion exchange membrane water electrolyzer, the catalyst demonstrates industrial-grade performance, sustaining 1 A cm^-2 at 1.85 V with remarkable stability over 1,000 h of continuous operation. Operando spectroscopic studies unveil that SO₄ ^2- leaching from surface Ni₃S₄ in the gradient structure provides dual protection against metal dissolution and chloride corrosion. Furthermore, the in situ formation of FeOOH synergistically stabilizes the catalytically critical Ni³⁺ species in NiOOH through strong Fe─O─Ni interfacial bonding, contributing to the exceptional durability. This work provides fundamental insights into corrosion-mediated catalyst design, offering a scalable pathway for developing industrial-grade electrocatalysts.