Operando Investigations of the Solid Electrolyte Interphase in the Lithium Mediated Nitrogen Reduction Reaction

The lithium-mediated nitrogen reduction reaction (Li-NRR) represents a promising approach for electrochemical nitrogen activation, in which the solid electrolyte interphase (SEI) layer formed on the electrochemically plated lithium plays a key role. Herein, we used time-resolved, operando, grazing incidence wide-angle X-ray scattering (GI WAXS) to identify SEI species and reaction intermediates in the Li-NRR, comparing LiBF4 and LiClO4 as electrolyte salts. We demonstrated how the SEI composition influences the Li-NRR performance by regulating proton transport to the plated Li. When LiBF4 is used as electrolyte salt, the formation of LiF and Lithium ethoxide (LiEtO) is observed. Reaction intermediates such as LiH and LiNxHy species were found and provide insight into reaction pathways towards undesired and desired products, respectively. Observed restructuring of the Cu (111) single crystal substrate also indicates interaction with plated Li that could possibly influence the Li-NRR performance. Together, these experiments give molecular insight on how to design Li-NRR systems and their SEI layers for optimal performance.