Ammonia-Promoted Lithium Redox-Mediated Nitrogen Reduction

Protonation of the lithium nitride intermediate is a critical step of the lithium redox-mediated nitrogen reduction reaction (Li-NRR), which is commonly provided by the ethanol proton carrier. While the field explores alternative, more stable H + shuttles, the capability of NH 3 to deliver protons for the conversion of Li 3 N into NH 3 and Li + has been majorly overlooked. Herein, we demonstrate a high ammonia yield rate of 350 ± 40 nmol s –1 cm –2 and faradaic efficiency of 93 ± 6% under 15 bar nitrogen in 6 h Li-NRR experiments when 0.08 M NH 3 is added to ethanol-free tetrahydrofuran solutions of 2 M lithium bis(trifluoromethylsulfonyl)imide electrolyte. Extended two-day-long experiments demonstrated the stability of the NH 3 -promoted Li-NRR, with only slightly decreased performance. In contrast, the introduction of NH 4 + suppresses the Li-NRR under these conditions. These results suggest that the proton shuttling during the Li-NRR might be provided by the reaction product, potentially enabling an important technological simplification.