Salt-Regulated Confinement of FeO Microcrystallites on Amorphous Mn₃CoO_x for Boosting Sustainable Acidic Water...

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 Mn₃CoO_x support confined FeO microcrystallites at a relatively low-temperature (623 K). The confined FeO microcrystallites showed strong interfacial electronic interactions with Mn₃CoO_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/Mn₃CoO_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 IrO₂ (∼ 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.