Understanding the Factors Determining the Faradaic Efficiency and Rate of the Lithium Redox-Mediated N₂ Reduction to Ammonia

Abstract

The lithium mediated reduction of N2 is one of the only available approaches to electrochemical ammonia production at significant yields under ambient conditions. However, much remains to be investigated about the various electrochemical processes and side reactions that are involved. Herein, we have examined the effects of parameters including electrode potential, convection, N2 pressure, and water content to refine and control the process. We demonstrate that a closely linear ammonia yield can be maintained during experiments up to 60 h in length, with approximately constant faradaic efficiency. This steady state operation appears to be preceded by a coating of the electrode surface with the products of the reductive electrolyte decomposition, such as LiF. We demonstrate ammonia yield rates above 1 nmol s–1 cm–2 and faradaic efficiencies as high as 60% through the improved control of the reaction conditions.