Lattice Strain in Au₃Cu Facilitated Hydrogen Spillover for Efficient Nitrate Electroreduction to Ammonia

Cu-based nanocatalysts have been widely studied for the electrochemical nitrate reduction reaction (NO₃RR) to ammonia, yet their activity and selectivity remain limited. Herein, we demonstrate that lattice-strained Au₃Cu, achieved by organizing Cu@Au₃Cu core-shell nanocrystals (NCs), facilitates efficient high-concentration nitrate electroreduction to ammonia. Typically, an NH₃ yield rate of 265.2 mg h^-1 mg_cat^-1 is achieved, which is superb among reported Cu-Au catalysts. In situ experiments confirm that the strained Au₃Cu promotes water dissociation under alkaline conditions, ensuring enhanced *H surface coverage to support efficient hydrogenation. Density functional theory (DFT) calculations further demonstrate the strain-induced upward shift of the d-band center strengthens NO₃^- adsorption and activation. More critically, the compressive strain within the Au₃Cu shell drastically contracts Au-Cu interatomic distances, which achieves a substantial reduction in the energy barrier for hydrogen spillover from Au to Cu sites. These integrated effects collectively lower the energy barrier (0.12 eV) for forming the key reaction intermediate *NHO during the rate-determining step, boosting the overall NO₃RR kinetics. Integrating the NO₃RR catalyst into a Zn-NO₃^- battery as the cathode achieves a power density of 5.91 mW cm^-2 and FE of 90.5% for NH₃ production, highlighting the potential for energy-efficient nitrate-to-ammonia conversion.