Dynamic Cu–Fe Dual Sites Steering Tandem e–/H+ Delivery for Efficient NH3 Electrosynthesis in Acid

The energy-intensive Haber-Bosch process for ammonia synthesis necessitates sustainable alternatives, electrochemical nitrate reduction (eNO3RR) is emerging as a promising route to address nitrate pollution. However, it faces a critical bottleneck: the low ammonia selectivity arising from competitive hydrogen evolution. Herein, we introduce copper carbon dots-supported iron phthalocyanine (Cu-CDs/FePc) - a electrocatalyst featuring dynamic Cu–Fe dual sites that steer tandem e–/H+ delivery for efficient NH3 electrosynthesis. It achieves an outstanding ammonia yield of 17.69 mg h–1 mgcat.–1 with a remarkable Faradaic efficiency of 91.0% at −0.7 V vs RHE in acid conditions, which surpasses many reported transition metal-based electrocatalysts for eNO3RR. In-situ FTIR spectroscopy and density functional theory (DFT) calculations elucidate that dynamic Cu–Fe dual sites orchestrate directional electron–proton relay chains through electronic complementarity: Electron-deficient Cu2+ centers intensify NO3– adsorption/activation, while electron-enriched Fe2+ sites drive *NO2 protonation, and interfacial charge shuttling initiates valence oscillations (Cu+/Cu2+ and Fe2+/Fe3+) effectively lower rate-determining step energy barrier, thereby boosting ammonia selectively while simultaneously suppressing hydrogen evolution. Furthermore, the catalyst exhibits robust stability over 100 h and practical versatility in zinc-air battery systems. This work presents a rational design strategy for high-performance eNO3RR catalysts, offering a significant advance toward efficient green ammonia synthesis and environmental remediation.