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.