Electroreduction of nitrogen with almost 100% current-to-ammonia efficiency

Beyond its use in the fertiliser and chemical industries1, ammonia is currently seen as a potential replacement for carbon-based fuels and as a carrier for worldwide transportation of renewable energy2. Implementation of this vision requires transformation of the existing fossil fuel based technology for NH3 production3 to a simpler, scale-flexible technology, such as the electrochemical lithium-mediated nitrogen reduction reaction (Li-NRR)3,4. This provides a genuine pathway from N2 to ammonia, yet is hampered by limited yield rates and efficiencies4-12. Here we investigate the role of the electrolyte in this reaction and present a high-efficiency, robust process enabled by compact ionic layering in the electrode-electrolyte interfacial region. The interface is generated by a high-concentration imide-based lithium salt electrolyte, enabling stabilised ammonia yield rates of 150±20 nmol s-1 cm-2 and current-to-ammonia efficiency closely approaching 100%. The ionic assembly formed at the electrode surface suppresses electrolyte decomposition and supports stable N2 reduction. Our study highlights the interrelation between the performance of the Li-NRR and the physicochemical properties of the electrode-electrolyte interface. We anticipate that these findings will guide the development of a robust, high-performance process for sustainable ammonia production.