Coupled NOx production and electrochemical conversion processes for sustainable ammonium synthesis from air

Renewable energy-powered decentralized Power-to-X modules can drive the decarbonization of chemical and fuel production, promoting a more sustainable energy landscape. Here, an Air-to-Ammonia system was developed using a commercial dielectric barrier discharge (DBD) plasma-based ozone generator to oxidize air and produce nitrogen oxide intermediaries (NO x /NO x − ). A multi-phase electrolyzer then converted NO x /NO x − to NH 4 + under ambient conditions, achieving an energy consumption of <100 kWh kg NH4+ −1 . By optimizing ozone generator parameters, a maximum NO x /NO x − production rate of 166.5 mmol h −1 was obtained. The coupled air oxidation-electrolyzer exhibited a high NH 4 + yield of ~1.3 mmol h −1 cm −2 at −2.5 V, which is 5.8 and 3.3 times higher than the electrolyzers with solely gaseous NO x or solely ionic NO x − supply with the same concentrations, respectively. This NO x /NO x − co-supply strategy enables efficient ammonium production from low-concentration NO x sources, contributing to sustainable agriculture and expanding the use of ammonia as a sustainable fuel in remote markets. Decentralized ammonia production is vital for sustainable agriculture and clean energy systems. However, current ammonia electrification is challenged by the inertness of N 2 or the low concentration of alternative nitrogen oxides (NO x ) feedstocks. We introduce an integrated air-to-ammonia system combining a commercial ozone generator with a multi-phase electrolyzer to convert ambient air into ammonia via NO x intermediates. This approach achieves high production rates and enables the co-utilization of gaseous NO x and ionic NO x − . Moreover, the electrolyzer system is also promising to convert industrial NO x flue gas into valuable fertilizer and fuel. This work supports circular nitrogen management and contributes to energy, environmental, and agricultural sustainability • Introduced the first air-to-ammonia system using a commercial ozone generator and a multi-phase electrolyzer for efficient gaseous and ionic NO x co-reduction. • Achieved industrial-scale ammonia production at 1.3 mmol h −1 cm −2 from low-concentration NO x at −2.5 V cell voltage. • Enabled continuous NO x − supply and enhanced NO x conversion for ammonia production at the optimized three-phase interface revealed by in situ characterizations. • Demonstrated dual benefits for sustainable agriculture and closed-loop ammonia fuel systems with proven economic viability.