Electrosynthesis of NH₃ from low-concentration NO on cascade dual-site catalysts in neutral media.

Abstract

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 an intriguing 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 (Fe_SAC), 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 mg_cat.^-1 under 1.0 vol% NO in neutral media, outperforming pure Fe_SAC (NH₃ yield rate: 444.2 µg h^-1 mg_cat.^-1, FE: 56.6%) and prior to systems operating under high NO concentrations. Notably, the high NH₃ yield of 3207.7 μg h^-1 mg_cat.^-1 is achieved in a membrane electrode assembly (MEA) electrolyzer under a 1.0 vol% NO. This work establishes an inspirational 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.