Paving an interfacial hydrogen superhighway via N-bridged Ru nanoparticles with Cu single atoms for efficient nitrate electroreduction to ammonia.

Electrocatalytic nitrate reduction to ammonia is strongly dependent on the availability of active hydrogen (*H). Either insufficient *H supply or excessive *H accumulation at the catalyst surface can compromise ammonia production and Faradaic efficiency. To address this challenge, a RuNP/Cu NC catalyst was developed by constructing N-bridged Ru nanoparticles on a carbon‑nitrogen support anchored by single-atom Cu. In this architecture, Ru nanoparticles generate *H and establish a hydrogen-transfer pathway across the Ru nanoparticles/Cu single atoms interface, thereby promoting nitrate enrichment and subsequent hydrogenation. The RuNP/Cu NC catalyst achieved an NH3 yield rate of 7.92 mg h-1 cm-2 with a Faradaic efficiency of 97.22%, together with an energy efficiency of 34.31%, far surpassing those of RuNP/NC (9.75%) and Cu NC (13.64%). Operando DRT analysis revealed accelerated interfacial charge-transfer kinetics on RuNP/Cu NC, facilitating hydrogen spillover from Ru sites to adsorbed NO3- species on neighboring Cu sites. In situ FTIR spectroscopy captured the key intermediate *NH2OH. Theory calculations further showed that the hydrogenation superhighway established at the strong metal-support (MSI) interactions interface lowers the hydrogenation energy barrier of NH2OH. This work establishes a hydrogen-regulated reaction pathway and demonstrates the advantages of MSI for efficient ammonia electrosynthesis.