Salt‐Regulated Confinement of FeO Microcrystallites on Amorphous Mn ₃ CoO _x for Boosting Sustainable Acidic Water Oxidation

ABSTRACT Nanomaterials with amorphous surface have attracted significant attention in the oxygen evolution reaction (OER), which still needs further investigations. In this work, we developed a novel Salt‐regulated confinement loading method to prepare amorphous Mn 3 CoO x support confined FeO microcrystallites at a relatively low‐temperature (623 K). The confined FeO microcrystallites showed strong interfacial electronic interactions with Mn 3 CoO x matrix (abundant defect sites and flexible local environments), enabling efficient charge transfer and enhanced intermediate stabilization for efficient OER in acidic media. The FeO/Mn 3 CoO x exhibits remarkable OER performance, with a low overpotential of 252 mV@10 mA cm −2 with a significantly lower Tafel slope of 79 mV dec −1 , outperforming the commercial IrO 2 (∼ 290 mV@10 mA cm −2 ). Mechanistic studies reveal that the incorporation of FeO microcrystallites, as electron reservoirs to stabilize high‐valence intermediates and facilitate continuous turnover, induces a synergistic transition from a purely lattice oxygen‐mediated mechanism (LOM) to a dual LOM and oxygen pathway mechanism (OPM).These results are well corroborated by in situ attenuated total reflection surface‐enhanced infrared spectroscopy, differential electrochemical mass spectrometry, and density functional theory calculations. Our work provides a robust strategy to design amorphous, non‐precious‐metal OER catalysts capable of stable operation in acidic media, offering a scalable route toward efficient hydrogen production.