Materials Chemistry

The Role of Ion Solvation in Lithium Mediated Nitrogen Reduction



Since its verification in just 2019, there have been numerous high-profile papers reporting improved efficiency of the lithium-mediated electrochemical nitrogen reduction system to make ammonia. However, the literature lacks a cohesive investigation systematically linking bulk electrolyte properties to electrochemical performance and Solid Electrolyte Interphase (SEI) properties. In this study, we vary electrolyte salt concentration and observe a transition from an unstable working electrode potential to working electrode potential stability and peak in Faradaic efficiency of 7.8 ± 0.5 % at 0.6 M LiClO4. The behaviour is linked to the formation of Solvent Separated Ion Pairs in the electrolyte through Raman spectroscopy. Time of Flight Secondary Ion Mass Spectrometry and X-Ray Photoelectron Spectroscopy reveal a more inorganic, and therefore more stable, SEI layer with increasing salt concentration. A drop in Faradaic efficiency is seen at concentrations higher than 0.6 M LiClO4, which is attributed to a combination of a loss in nitrogen solubility and diffusivity as well as increased SEI conductivity as measured by Electrochemical Impedance Spectroscopy.


Thumbnail image of The Role of Ion Solvation in Lithium Mediated Nitrogen Reduction_ChemrXiv submission.pdf

Supplementary material

Thumbnail image of 220804 The role of ion solvation in lithium mediated nitrogen reduction_SI_FINAL for chemrxiv.pdf
The Role of Ion Solvation in Lithium Mediated Nitrogen Reduction: Supplementary Information
Information on experimental procedures