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.