Electrosynthesis of ammonia with high selectivity and high rates via engineering of the solid-electrolyte interphase

Ammonia is a large-scale commodity essential to fertilizer produc-tion, but the Haber-Bosch process leads to massive emissions of car-bon dioxide. Electrochemical ammonia synthesis is an attractive alternative pathway, but the process is still limited by low ammonia production rate and faradaic efficiency. Herein, guided by our theoretical model, we present a highly efficient lithium -mediated process enabled by using different lithium salts, leading to the formation of a uniform solid-electrolyte interphase (SEI) layer on a porous copper electrode. The uniform lithium-fluoride -enriched SEI layer provides an ammonia production rate of 2.5 +/- 0.1 mmol s-1 cmgeo-2 at a current density of-1 A cmgeo-2 with 71% +/- 3% faradaic efficiency under 20 bar nitrogen. Experi-mental X-ray analysis reveals that the lithium tetrafluoroborate elec-trolyte induces the formation of a compact and uniform SEI layer, which facilitates homogeneous lithium plating, suppresses the un-desired hydrogen evolution as well as electrolyte decomposition, and enhances the nitrogen reduction.

Automated summary

In this study, a highly efficient lithium-mediated ammonia synthesis process was proposed, which could enhance the ammonia production rate and faradaic efficiency by forming a uniform solid-electrolyte interphase (SEI) layer on a porous copper electrode.