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

Dynamic structural and phase evolution commonly occur during electrochemical nitrate (NO₃ ^-) 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 NH₃ synthesis. In this study, starting from a CuO/CoO_X (Co₁Cu₉O_X) pre-catalyst, an adaptively reconstructed heterojunction (R-Co₁Cu₉O_X) with mainly Cu/CoO_X is rationally engineered, synergistically catalyzing NO₃ ^-RR involving multiple intermediates. At -0.2 V vs. RHE, optimized R-Co₁Cu₉O_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 NO₃ ^-RR catalysis under dynamic changes in the chemical state of Cu.