Fenton like Reactivity on Fe₃O₄ Nanozymes Driven by Charge Transfer and Interfacial Water

Magnetite (Fe₃O₄) nanoparticles, widely recognized as inorganic nanozymes due to their enzyme like catalytic activity, are emerging as effective heterogeneous catalysts for Fenton like reactions, in which lattice iron activates hydrogen peroxide (H₂O₂) togenerate reactive oxygen species. While hydroxyl radicals (•OH) are generally con- sidere d the primary reactive species, the underlying mechanism particularly the possible involvement of a high valent ferryl intermediate (Fe⁴+=O)- remains under de- bate. Here, we combine surface specific spectroscopy with density functional theory (DFT) calculations to elucidate the mechanism of H₂O₂ activation on Fe₃O₄ surfaces. We find that •OH production is driven by electron transfer from subsurface Fe²⁺ centers to adsorbed H₂O₂ accompanied by the transient formation of a ferryl species. Moreover, interf acial water plays an active role in modulating surface reactivity and stabilizing key reaction intermediates. These findings clarify the origin of radical formation in Fe₃O ₄ nanozymes and offer mechanistic insight to guide the rational design of next gener ation oxide based catalysts for environmental and biomedical applications.