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 NH3 to deliver protons for the conversion of Li3N into NH3 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 NH3 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 NH3-promoted Li-NRR, with only slightly decreased performance. In contrast, the introduction of NH4+ 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.