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Artificial ammonia synthesis is vital to modern life; however, the Haber-Bosch process, by which most ammonia is synthesized, is capital and carbon intensive. Zero-valent-metal-mediated ammonia synthesis is a promising alternative but requires a metal that is both a strong reductant and forms a stable nitride. Only a small number of metals, like lithium, can satisfy these constraints. Therefore, we developed an electrochemical paradigm enabling the use of different reductants by orthogonalizing the roles of the zero-valent metal between sodium metal and a Ti active site. These components are cheaper than lithium by two orders of magnitude. Using a sodium-naphthalene-titanium cascade, we achieved a rate of 475 nmol cm-2 s-1 and a Faradaic efficiency of 24% and found that the reaction rate depends primarily on current density. 

The lithium-mediated nitrogen reduction reaction (LiNRR) produces ammonia in ambient conditions. This electrochemical pathway is dependent on a catalytic solid–electrolyte interphase—a nanoscale passivation layer formed from reductive electrolyte decomposition on the surface of lithium metal. The catalytic solid–electrolyte interphase is a unique nanostructured environment that exists on reactive metal surfaces and intimately influences product selectivity. Here we explore recent progress made in the field of lithium-mediated nitrogen reduction to ammonia, especially in light of growing knowledge about the nature of the catalytic solid–electrolyte interphase. We systematically analyse the observed chemical species and reactions that occur within the solid–electrolyte interphase. We also summarize key developments in kinetic and transport models, as well as highlight the cathodic and complementary anodic reactions. Trends in ammonia selectivities and rates with varying electrolyte compositions, cell designs and operating conditions are extracted and used to articulate a path forward for continued development of lithium-mediated nitrogen reduction to ammonia.