Adaptive Cu Reconstruction in Heterostructure Drives High‐Rate Nitrate‐to‐Ammonia Conversion

ABSTRACT Dynamic structural and phase evolution commonly occur during electrochemical nitrate (NO ₃ ⁻ ) reduction, leading to the formation of catalytically favorable active phases, particularly in mixed‐valence metal species. However, large overpotentials and the accumulation of undesired byproducts still severely limit the efficiency of NH ₃ synthesis. In this study, starting from a CuO/CoO _X (Co ₁ Cu ₉ O _X ) pre‐catalyst, an adaptively reconstructed heterojunction (R‐Co ₁ Cu ₉ O _X ) with mainly Cu/CoO _X is rationally engineered, synergistically catalyzing NO ₃ ⁻ RR involving multiple intermediates. At −0.2 V vs. RHE, optimized R‐Co ₁ Cu ₉ O _X delivers an ammonia yield of 54.68 mg h ⁻¹ mg _cat ⁻¹ with a Faradaic efficiency of 95.40%. Structural analyses reveal that Cu species undergo a self‐adaptive reconstruction equilibrium involving a surface‐localized hydroxylated oxidized Cu species coupled with reduced metallic Cu domains. Such adaptive evolution promotes nitrate adsorption and stabilizes key nitrogen‐containing intermediates. Meanwhile, the dual‐phase heterogeneous interface optimizes interfacial *H supply, ensuring precise regulation of the adsorption and hydrogenation of nitrogen‐containing intermediates. This heterostructure engineering with self‐adaptive reconstruction offers a promising strategy for advanced NO ₃ ⁻ RR catalysis under dynamic changes in the chemical state of Cu.