Self‐Sustaining Dynamic Alkaline Microenvironment‐Mediated Efficient Nitrate Electroreduction to Ammonia on MnFeO x in Neutral Electrolyte

Electrocatalytic nitrate reduction (NO 3 RR) that utilizing renewable electricity to convert nitrate pollutants in wastewater, represents a promising route for sustainable ammonia synthesis, yet its efficiency in neutral media is severely limited by sluggish kinetics and intense competition from hydrogen evolution reaction (HER). Herein, we introduce a “self‐sustaining alkaline local microenvironment” strategy enabled by a MnFe dual‐site oxide that concurrently serves as a structural scaffold and catalytic mediator, in which inactive Fe Oh sites in FeO x are selectively substituted by Mn while active Fe Td sites are retained. Fe sites in 1D MnFeO x activate NO 3 − and dynamically capture OH − to form FeOOH, establishing a localized alkaline microenvironment around the active sites at electrode—electrolyte interface that effectively suppresses HER. Concurrently, Mn sites stabilize the high‐valent Fe species and continuously split interfacial H 2 O into OH − and H*, ensuring the robust persistence of the alkaline microenvironment. The resulting 1D MnFeO x catalyst delivers an NH 3 Faradaic efficiency of 95.9% (12.3 mg h −1 cm −2 ) in neutral media and operates stably for over 20 h without degradation. By advancing local pH regulation from external intervention to intelligent self‐regulation, this work offers a new insight in adaptive electrocatalyst design and regulating the interfacial microenvironment beyond NO 3 RR.