Ionomer-Regulated Cu/Co Tandem Catalysis for Efficient Electrochemical Nitrate-to-Ammonia Conversion

Electrochemical nitrate reduction to ammonia offers a sustainable route for nitrogen fixation, yet achieving high efficiency and selectivity remains challenging. Here, a Sustainion-enabled Cu/Co tandem catalyst is developed to couple compositional synergy with ionomer-mediated interfacial regulation. The optimized Cu60Co40/Sus/C electrode delivers a Faradaic efficiency of 91.3% and an NH3 yield rate of 2.63 mmol gcat.−1 h−1 at −0.3 V vs. RHE, surpassing Cu-Co/Nafion/C and Cu-Co/C counterparts. Structural analyses confirm that Sustainion prevents nanoparticle aggregation and maintains robust Cu/Co interfaces. Electrochemical and in situ spectroscopic studies reveal that the cationic quaternary ammonium groups of Sustainion electrostatically enrich NO3−/NO2− intermediates, facilitating their adsorption and hydrogenation toward NH3 formation. The combined structural stabilization and intermediate modulation enable efficient tandem catalysis between Cu-driven nitrate activation and Co-mediated hydrogenation. This work provides molecular-level insight into ionomer–catalyst interactions and highlights interfacial engineering as a powerful strategy for sustainable ammonia synthesis.