Cascade dual-sites enable low-concentration NO-to-NH3 electrosynthesis in neutral media

Electrosynthesis of NH3 from low-concentration NO (NORR) in neutral media offers a sustainable nitrogen fixation strategy but is hindered by weak NO adsorption, slow water dissociation, and sluggish hydrogenation kinetics. Herein, we propose a new strategy that successfully overcomes these limitations through using an electron-donating motif to modulate NO-affinitive catalysts, thereby creating dual active site with synergistic functionality. Specifically, we integrate electron-donating nanoparticles into a Fe single-atom catalyst (FeSAC), where Fe sites ensure strong NO adsorption, while electron-donating motifs promote water dissociation and NO hydrogenation. In situ X-ray absorption spectroscopy (XAS), in situ attenuated total reflection-infrared spectroscopy (ATR-IR), and theoretical calculations reveal that electron-donating motifs increase Fe site electron density, strengthening NO adsorption. Additionally, these motifs also promote water dissociation, supplying protons to lower the NO hydrogenation barrier. This synergistic interplay enables a cascade reaction mechanism, delivering a remarkable Faradaic efficiency (FE) of 90.3% and a NH3 yield rate of 709.7 µg h-1 mgcat.-1 under 1.0 vol% NO in neutral media, outperforming pure FeSAC (NH3 yield rate: 444.2 µg h-1 mgcat.-1, FE: 56.6%) and prior high-NO-concentration systems. Notably, a record NH3 yield of 3123.8 μg h-1 mgcat.-1 was achieved in a membrane electrode assembly (MEA) electrolyzer under a 1.0 vol% NO. This work establishes a new paradigm in NORR by simultaneously enhancing NO adsorption, water dissociation, and hydrogenation kinetics, providing a scalable route for efficient NH3 electrosynthesis from dilute NO sources.