Reorganization of Interfacial Water by Cu–Ru Interfaces for Efficient Nitrate-to-Ammonia Electrosynthesis

Electrocatalytic nitrate reduction offers a sustainable route for ammonia (NH3) synthesis, yet its efficiency is limited by sluggish N–O bond cleavage, incomplete NOx hydrogenation, and competing hydrogen evolution reaction. However, how catalyst structural engineering regulates the interfacial microenvironment remains unclear, despite its critical importance for constructing efficient catalysts. Here, we report a Cu3Ru7 catalyst with abundant Cu–Ru interfaces, where interface-induced water reorganization enables efficient NH3 production. The Cu3Ru7 catalyst exhibits an impressive NH3 formation rate of 19.7 mmol h–1 cm–2 at 5 A cm–2 in a membrane electrode assembly (MEA) electrolyzer and remains stable at 2 A cm–2 with an NH3 Faradaic efficiency of ∼86% for 500 h. A scale-up demonstration using a 100 cm2 MEA electrolyzer affords an NH3 formation rate up to 1.5 mol h–1 at 400 A. The in situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) reveals that Cu3Ru7 catalyst establishes a moderate interfacial hydrogen-bond network, which creates a water-mediated interfacial micro environment that facilitates NOx deoxygenation and subsequent NHx formation. Ab initio molecular dynamics (AIMD) simulations further reveal that the Cu–Ru interface stabilizes the dissociating oxygen atom through a persistent and dynamically connected hydrogen-bond network, thereby facilitating sequential NO3– → NO2 → NO conversion. Meanwhile, the surrounding Cu matrix attenuates the excessive *H accumulation characteristic of Ru, suppressing the hydrogen evolution reaction. This work establishes Cu–Ru interface-induced interfacial water reorganization as a strategy for improving electrocatalytic nitrate reduction performance.