Pathway toward Scalable Energy-Efficient Li-Mediated Ammonia Synthesis.

Lithium-mediated ammonia synthesis (LiMAS) is an emerging electrochemical method for NH 3 production, featuring a meticulous three-step process involving Li + electrodeposition, Li nitridation, and Li 3 N protolysis. The essence lies in the electrodeposition of Li + , a critical phase demanding current oscillations to fortify the solid-electrolyte interface (SEI) and ensure voltage stability. This distinctive operational cadence orchestrates Li nitridation and Li 3 N protolysis, profoundly influencing the NH 3 selectivity. Increasing N 2 pressure enhances the NH 3 faradaic efficiency (FE) up to 20 bar, beyond which proton availability controls selectivity between Li nitridation and Li 3 N protolysis. The proton donor, typically alcohols, is a key factor, with 1-butanol observed to yield the highest NH 3 FE. Counterion in the Li salt is also observed to be significant, with larger anions (e.g., exemplified by BF 4 - ) improving SEI stability, directly impacting LiMAS efficacy. Notably, we report a peak NH 3 FE of ∼70% and an NH 3 current density of ∼-100 mA/cm 2 via a delicate balance of process conditions, encompassing N 2 pressure, proton donor, Li salt, and their respective concentrations. In contrast to the recent literature, we find that the theoretical maximum energy efficiency of LiMAS hinges significantly on the proton source, with LiMAS utilizing H 2 O calculated to have a maximum achievable energy efficiency of 27.8%. Despite inherent challenges, a technoeconomic analysis suggests high-pressure LiMAS to be more feasible than both ambient LiMAS and a modified green Haber-Bosch process. Our analysis finds that, at a 100 mA/cm 2 NH 3 current density and a 6 V cell voltage, LiMAS delivers green NH 3 at an all-inclusive cost of $456 per ton, significantly lower than conventional cost barriers. Our economic analysis underscores high-pressure LiMAS as a potentially transformative technology that may revolutionize large-scale NH 3 production, paving the way for a sustainable future.