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 mg_cat.^-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.