Interfacial Electronic Modulation in Upcycled Heterostructures MZVI@Fe 3 O 4 for Tandem NO Oxidation and Valorization

The tandem conversion of nitrogen oxides (NO x ) from industrial emissions into value‐added ammonia (NH 3 ) represents a compelling strategy for restoring the global nitrogen cycle. Herein, we establish a sustainable “waste‐to‐treasure” paradigm by upcycling industrial copper slag into a robust micron‐sized zero‐valent iron (MZVI@Fe 3 O 4 ) heterojunction, effectively liberating iron active sites from inherent silicate constraints via mineral phase reconstruction. Experimental and density functional theory (DFT) investigations reveal that the self‐regulated, dynamically thickening Fe 3 O 4 interlayer acts as a critical mediator for interfacial electronic modulation. This structural evolution downshifts the d‐band center and enhances localized Lewis acidity, driving a robust electron withdrawal from H 2 O 2 . Consequently, this oxidative deprotonation strategically shifts H 2 O 2 activation from • OH‐dominated homolytic cleavage to O 2 •− ‐driven heterolytic cleavage, facilitating the rapid, one‐step oxidation of NO to nitrate by preventing intermediate poisoning. Leveraging the rapid interfacial electron transfer of this heterostructure, the generated nitrate is subsequently electroreduced to NH 3 with an impressive Faradaic efficiency of 90.2%. Furthermore, Life Cycle Assessment (LCA) confirms a substantially lowered environmental footprint compared to conventional technologies. This work provides fundamental atomic‐level insights into interfacial electronic modulation and opens a closed‐loop route for metallurgical solid waste valorization.