Lattice Strain in Au ₃ Cu 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 mgcat–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.