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

In addition to its use in the fertilizer and chemical industries 1 , ammonia is currently seen as a potential replacement for carbon-based fuels and as a carrier for worldwide transportation of renewable energy 2 . Implementation of this vision requires transformation of the existing fossil-fuel-based technology for NH 3 production 3 to a simpler, scale-flexible technology, such as the electrochemical lithium-mediated nitrogen-reduction reaction 3 , 4 . This provides a genuine pathway from N 2 to ammonia, but it is currently hampered by limited yield rates and low efficiencies 4 – 12 . Here we investigate the role of the electrolyte in this reaction and present a high-efficiency, robust process that is enabled by compact ionic layering in the electrode–electrolyte interface region. The interface is generated by a high-concentration imide-based lithium-salt electrolyte, providing stabilized ammonia yield rates of 150 ± 20 nmol s −1 cm −2 and a current-to-ammonia efficiency that is close to 100%. The ionic assembly formed at the electrode surface suppresses the electrolyte decomposition and supports stable N 2 reduction. Our study highlights the interrelation between the performance of the lithium-mediated nitrogen-reduction reaction 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.