Steric Hindrance-Derived Li+ Solvation to Enhance Lithium-Mediated Nitrogen Reduction

Abstract

This study proposes a steric hindrance-derived electrolyte (STE) to generate Li⁺ anion-rich solvation structures to enhance the Li-mediated nitrogen reduction reaction (Li-NRR), a promising electrochemical green ammonia synthesis method. The STE applied methylation of the alpha proton in the tetrahydrofuran (THF) solvent, which dissolved lithium salts, leading to the weak solvation of Li⁺ and generating an anion-rich-solvated structure. The resultant anion-derived solid electrolyte interphase with thin and uniform inorganic properties improved the selectivity, energy efficiency (EE), and stability of the Li-NRR process. Additionally, the anion-rich solvation exhibited antireduction stability and inhibited electrolyte decomposition. Consequently, the STE achieved a 2-fold increase in Faradaic efficiency and NH₃ yield rate (65.8% and 90.8 nmol cm^–2 s^–1, respectively) compared to the THF-single electrolyte (35.7% and 49.3 nmol cm^–2 s^–1) while increasing the EE by 1.5 times.