Dual-sites for low-concentration NO to NH3 electrosynthesis in neutral media: promoting NO adsorption and water dissociation

The electrosynthesis of NH3 from low-concentration NO (NORR) in neutral media is a promising strategy for sustainable nitrogen fixation. However, the inherently weak adsorption of NO on traditional catalysts, coupled with the challenging water dissociation and NO hydrogenation kinetics, limits the efficiency of this reaction. Herein, we introduce a novel strategy by loading Pt nanoparticles (PtNPs) as electron donor onto an Fe single-atom catalyst (FeSAC) to form a strong electronic interaction between PtNPs and FeSAC. This electronically engineered architecture creates dual active site that significantly improves neutral low concentration NORR performance. In situ X-ray absorption spectroscopy (XAS), in situ attenuated total reflection-infrared spectroscopy (ATR-IR), and theoretical calculations reveal that PtNPs, acting as an electron reservoir, donate electrons to the FeSAC sites. This electron donation increases electron density at the Fe sites, promoting NO adsorption. Additionally, the PtNPs facilitate water dissociation, providing protons that greatly decrease the activation barrier for NO hydrogenation. Thus, the PtNPs/FeSAC dual-sites activated a synergistic cascade mechanism in neutral media during NORR process, with a Faradaic efficiency (FE) of 90.3% and an NH3 yield rate of 709.7 µg h-1 mgcat.-1 under 1.0 vol% NO, outperforming pure FeSAC (NH3 yield rate: 444.2 µg h-1 mgcat.-1, FE: 56.6%) and previously reported systems operating at high NO concentrations. Remarkably, this neutral NORR process achieved a record NH3 yield of 3023.8 μg h-1 mgcat.-1 in a membrane electrode assembly (MEA) electrolyzer under a 1.0 vol% NO atmosphere. This work develops a new class of electron-donating nanoparticles-mediated dual-sites that simultaneously enhance NO adsorption and facilitate water dissociation, significantly improving neutral low concentration NORR performance and paving the way for large-scale sustainable NH3 electrosynthesis.