Bridging Cobalt Single Atom Satellite and Nanoparticle Synergies for Efficient Low-Concentration NO Electroreduction to Ammonia

The electrochemical nitric oxide reduction reaction (NORR) provides a promising pathway for mitigating air pollutant NO while generating valuable ammonia (NH3). However, most research has focused on high NO concentrations (≥10%), which contrast with industrial dilute streams (≤1%), where conventional catalysts, such as single-atom catalysts (SACs), struggle with insufficient active site density and limited *H supply, while nanoparticle catalysts suffer from hydrogen evolution reaction (HER) competition. To address these challenges, we designed a hybrid catalyst consisting of atomically dispersed Co–N4 satellitic sites and Co(111) nanoparticles (Co SA-NPs). Through electronic interaction, Co(111) facilitated enhanced water dissociation to generate *H, while Co–N4 sites strengthened NO adsorption and activation. This cooperative mechanism promoted rapid *H spillover, enabling selective NO hydrogenation to NH3 while suppressing HER. Under 1% NO, Co SA-NPs achieved a significant NH3 yield rate of 11389 μg cm–2 h–1, which is 2.6 to 243.9 times higher than all previously reported NORR catalysts. At industrially relevant and ultralow concentrations (0.05, 0.1, and 0.5%), it maintains a notable average Faradaic efficiency of 93.6% and NH3 yield rates (556, 948, and 3120 μg cm–2 h–1 respectively) among the highest reported under such challenging conditions. Furthermore, the catalyst demonstrated durability with >85 h of stable operation, and a cumulative NH3 production reaching the gram-scale, showcasing its practical potential. Techno-economic analysis (TEA) revealed that NORR with Co SA-NPs could achieve zero-cost NO treatment and even generate profit, compared to traditional NH3–SCR.