Cr-Leaching Induced Vacancy Engineering for High-Performance Anion Exchange Membrane Water Electrolysis

Anion exchange membrane water electrolysis (AEMWE) offers a compelling route to large-scale green hydrogen production. However, developing catalysts that simultaneously combine high activity, long-term durability, and stack-level scalability remains a major challenge. Here, we report a magnetron-sputtered NiFeCr₂ thin-film catalyst that delivers 3 A cm^{- 2} at 1.77 V and 8.54 A cm^{- 2} at 2.10 V in an AEMWE membrane electrode assembly at 60°C, while maintaining stable operation at 2 A cm^{- 2} for 1798 h. Notably, the thin-film catalyst was further assembled into a 15 × 100 cm² electrolyzer stack, delivering a peak power of 12.87 kW and validating its practical scalability. In situ spectroscopic characterization and electrochemical mechanistic studies reveal that electrochemical reconstruction induces partial Cr dissolution and the concomitant formation of active Ni/FeOOH phases, while confirming that NiFeCr₂ operates via a lattice-oxygen-mediated mechanism. Density functional theory calculations indicate Cr vacancies increase metal-oxygen covalency, strengthen adsorption of oxygenated intermediates, and lower free energy barriers for oxygen evolution reaction.