Ammonia production via electrochemical dinitrogen reduction: addressing parameters control in the metal-mediated systems Anna Mangini , Noemi Pirrone, Sara Garcia-Ballesteros, Federico Bella Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 - Turin, Italy Ammonia (NH 3 ) is recently gaining interest as a carbon-free fuel, particularly in maritime applications, thanks to its superior energy density in comparison with hydrogen (H 2 ), i.e ., 12.9 MJ L –1 vs 2.76 MJ L –1 , and compatibility with existing infrastructure. [1] However, NH 3 production relies almost exclusively on the Haber-Bosch process, which operates under extreme conditions (400–500 °C, 150–300 bar), resulting in a global average ratio of about 2.5 tons of carbon dioxide emitted per ton of NH 3 produced. [2] Moreover, the global NH 3 production, which already exceeds 450 million tons per year, is predicted to increase alongside the demographic growth and the related fertilizer demand, and the Haber-Bosch plants are usually centralized to maximize the efficiency. [3] Therefore, the coupling of this process with green H 2 production and with renewable energy sources presents many challenges. Indeed, NH 3 obtained from dinitrogen (N 2 ) intrinsically depends on H 2 production , which is nowadays derived from steam methane reforming. In this scenario, the development of a fully electrified N 2 -to-NH 3 pathway is critical to decarbonize the NH 3 production and enabling its role as a sustainable fuel. Research on electrochemical N 2 reduction has been slowed by particularly low selectivity and production, leading to limited Faradaic efficiency (FE). Recently, the emerging lithium-mediated strategy in aprotic media achieved 300 h of continuous operation with a FE as high as 64%. [4] This system leverages the lithium singular ability of both activate N 2 and stabilize the intermediate, enabling simultaneous protonation at ambient conditions. [5] While promising, scalability and long-term stability remain unresolved. This study starts from the recent advancements in the lithium-mediated NH 3 electrosynthesis, emphasizing the effect of different process parameters and of the electrolyte engineering. In particular, the electrolyte composition and the electrochemical protocol were studied by means of different analytical and statistical tools, e.g ., the design of experiment combined with the surface response methodology. [6] The interplay between the factors will be deepened for a rational system optimization. The findings underscore the potential of NH 3 electrosynthesis, opening up to a sustainable energy vector, while identifying critical areas for future research. This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 948769, project title: SuN 2 rise). References 1. G. Jeerh, M. Zhang, S. Tao, J. Mater. Chem. A 2021 , 9 , 727–752. 2. M. Wang, M. A. Khan, I. Mohsin, J. Wicks, A. H. Ip, K. Z. Sumon, C. T. Dinh, E. H. Sargent, I. D. Gates, M. G. Kibria, Energy Environ. Sci. 2021 , 14 , 2535–2548. 3. D. R. MacFarlane, P. V. Cherepanov, J. Choi, B. H. R. Suryanto, R. Y. Hodgetts, J. M. Bakker, et al. , Joule 2020 , 4 , 1186– 1205. 4. S. Li, Y. Zhou, X. Fu, J. B. Pedersen, M. Saccoccio, S. Z. Andersen, et al. , Nature 2024 , 629 , DOI 10.1038/s41586-024- 07276-5. 5. A. Mangini, L. Fagiolari, A. Sacchetti, A. Garbujo, P. Biasi, F. Bella, Adv. Energy Mater. 2024 , 14 , 2400076. 6. A. Mangini, J. M. V. Bjarke, S. Garcia Ballesteros, A. Pedico, M. Armandi, F. Bella, Angew. Chem. Int. Ed. 2025 , 64 , e202416027.
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