In Situ Dynamically Reconstructed Metastable CoO/Co‐Cu ₂ O/Cu Heterointerface for Cascade Electro‐Reduction of Nitrate With Concurrent Ammonia Recovery

ABSTRACT Electrocatalytic nitrate reduction reaction (e‐NO 3 RR) offers a promising strategy for converting NO 3 − ‐N contaminants into NH 3 . Cu‐based catalysts have leading advantages in e‐NO 3 RR, however, they are hindered by weak NO 2 − adsorption, inefficient intermediates utilization, and sluggish kinetics of subsequent hydrogenation, particularly at low‐concentration NO 3 − . Herein, the metastable CoO/Co‐Cu 2 O/Cu heterointerface is in situ dynamically reconstructed from the initial Co‐Cu 2 O lotus‐root‐shaped nanorods to facilitate cascade e‐NO 3 RR for NH 3 production, achieving an NH 3 yield rate of 9.35 mg h −1 cm −2 and a Faradaic efficiency of 94.3% at −0.7 V vs. RHE under environmentally relevant NO 3 − levels. Operando spectroscopic techniques and theoretical calculations elucidate a synergistic effect between the in situ reconstructed transient Cu 2 O/Cu and CoO/Co active sites. Specifically, the dynamically evolved Cu 2 O/Cu moieties facilitate the adsorption and conversion of * NO 3 − to * NO 2 − , while the in situ formed CoO/Co species modulate the * NO 2 adsorption energy and the electronic structure of dynamic Cu 2 O/Cu, thereby enhancing active hydrogen generation for nitrogenous intermediates hydrogenation. Using a hydrophobic membrane‐mediated acid adsorption process, high‐purity solid (NH 4 ) 2 SO 4 was successfully acquired from the e‐NO 3 RR effluent of actual NO 3 − ‐containing wastewater. Our findings provide a foundation for the rational design of high‐efficiency NO 3 − ‐to‐NH 3 conversion electrocatalysts through interface engineering approaches and establish a dynamic structure‐activity relationship research paradigm.