Electrocatalytic nitrate reduction (NO3RR) to ammonia presents a sustainable route for pollutant remediation and green synthesis, yet challenges persist in achieving high efficiency and selectivity. Herein, we report a cobalt-doped copper aerogel (Cu95Co5) synthesized via one-step co-reduction, demonstrating exceptional NO3RR performance with 94.91% faradaic efficiency at –0.6 V and 31.15 mg mgcat–1 cm–2 h–1 NH3 yield at –0.7 V vs. RHE. The system achieves an impressive energy efficiency of 31.03% and enables a record-low ammonia production cost of $0.53 kg–1. Multiscale characterization reveals that Co doping induces lattice contraction, optimizes d-band positioning, and enhances interfacial K+·H2O interactions, collectively promoting water dissociation and *H generation. The combination of operando spectroscopies (SERS, ATR-FTIR, DEMS) and density functional theory (DFT) calculations elucidate a stepwise hydrogenation pathway: *NO3 → *NO2 → *NO → *NH2OH → *NH3, with the rate-determining step (RDS) identified as *NO hydrogenation to *NHO. The hierarchical porosity of the aerogel facilitates mass transport while Cu-Co synergy suppresses hydrogen evolution reactions via electronic modulation. Practical viability is demonstrated through stable 12-hour operation in a Zn-NO3– battery. This work provides insights into Cu-Co catalysis and establishes design principles for high-performance NO3RR systems.
