Enhancing Lithium-Mediated Nitrogen Reduction with Porous Polymer Fibers Featuring Lithium-Ion Affinity

Abstract

The interaction between the electrolyte and working electrode surface affects the cascade of reactions involving Li deposition, N₂, and proton carriers and consequently the NH₃ production from Li-mediated nitrogen reduction reaction (Li-NRR). Efficient Li-NRR at low Li concentrations is particularly challenging because of low current density and uneven Li metal and lithium nitride plating. Here, the enhanced electrochemical production of NH₃ for a low Li concentration of 0.5 m are demonstrated by employing 3D porous polymer fibers featuring Li⁺-affinity on Cu electrodes. Raman and IR spectroscopic analyses exhibit that the polymeric fibers composed of carboxyl and hydroxyl groups can form Li-binding complexes and decrease interactions with solvents and anions in the electrolyte. The electrochemical analyses support that this polymeric porous structure serves to retain Li⁺ near the electrode, expanding the active surface area and increasing current density. The Li-affinitive polymer fibers are effective even at a low Li salt concentration of 0.5 m to improve NH₃ yield and Faradaic efficiency. This study underscores the importance of porous morphology, Li affinity, and its analytical methods in understanding Li-NRR.