Suppressing Anion Repulsion for Enhancing Li-Mediated Nitrogen Reduction

Electrochemical lithium-mediated nitrogen reduction (Li-NRR) presents a sustainable alternative to Haber–Bosch for ammonia synthesis. Efficiency and stability are critically governed by the solid electrolyte interphase (SEI), which regulates reactant transport and suppresses side reactions. While anion-derived SEI formed under anion-rich solvation is beneficial, conventional electric double layer (EDL) repel anion at the cathode, limiting favorable SEI formation. Therefore, this study introduces cationic ionomer additives that form a positively charged ionic interfacial layer, mitigating anion repulsion and reducing interfacial solvent accumulation. An imidazolium (C 3 H 4 N 2 )-functionalized cation ionomer enables the formation of a tailored EDL, achieving a Faradaic efficiency and ammonia yield of 92 ± 3% and 58 ± 4 nmol s –1 cm –2, markedly surpassing the conventional EDL (63 ± 7%, 28 ± 9 nmol s –1 cm –2 ). A significant decrease in anion repulsion was confirmed via computational and in situ spectroscopic analyses. The demonstrated applicability across various lithium salts clearly reveals the overall effectiveness of this cationic ionomer-based EDL engineering in Li-NRR.