Highly Selective Electrocatalytic Ammonia Synthesis Enabled by Spatial Separation of Active Hydrogen Capture and Spillover Sites.

Electrochemical nitrate reduction (eNO3RR) enables sustainable ammonia (NH3) synthesis and nitrate (NO3 -) remediation but is limited by sluggish multi-step proton-electron transfers and inefficient intermediate conversion. To address these challenges, we strategically manage the generation and utilization of active hydrogen (H*) by integrating metallic Cu with atomically dispersed Zn-N4 sites, thereby selectively increasing NH3 production. In situ x-ray absorption spectroscopy, in situ infrared, in situ Raman, and combined with theoretical calculations, systematically demonstrate that Zn-N4 sites facilitate water dissociation to generate and capture H* species. These H* species subsequently spill over to neighboring metallic Cu, which play a crucial role in NO3 - adsorption and activation. The spatial separation effect between H* capture and utilization sites ensures continuous H* generation and supply, thus enhancing N─H bond coupling for efficient NH3 synthesis. As a result, the catalyst achieves a maximum NH3 yield rate of 21.96 mg h-1 cm-2 and a highest Faradaic efficiency (FE) of 97.07% in 0.1 M KNO3 under alkaline media. The constructed Zn-NO3 - battery can deliver an impressive power density of 14.59 mW cm-2, a NH3 yield rate of 4.26 mg h-1 cm-2, and a FE of 93.65%, while consistently operating for over 100 h.