The Effect of Applied Potential on the Li-mediated Nitrogen Reduction Reaction Performance.

Izelaar, Boaz; Karanth, Pranav; Toghraei, Arash; Pal, Santosh K; Girichandran, Nandalal; Weijers, Mark; Hendrikx, Ruud W A; Mulder, Fokko M et al. · Nat Commun · 2025

basic_science · Level V

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Abstract

The Li-mediated nitrogen reduction reaction (Li-NRR) has been proposed as one of the most promising ambient production routes for green ammonia. However, the effect of the applied potential (E<sub>we</sub>) on the reaction performance and the properties of the solid electrolyte interphase (SEI) remain poorly understood. Herein, we combine potential controlled experiments using a reliable Li<sub>x</sub>FePO<sub>4</sub> based reference electrode with post-mortem SEI characterization techniques, wherein we observe both an increase in the LiF concentration in the SEI, originating from LiTFSI decomposition, and the Faradaic efficiency (FE<sub>NH3</sub>) with an increasing E<sub>we</sub>. The transition from a predominantly organic SEI at low E<sub>we</sub> (-3.2 V<sub>SHE</sub>) to a LiF-enriched layer at higher E<sub>we</sub> indicates the existence of kinetic barriers for the SEI formation reactions. Moreover, thicker and denser SEI structures observed at a higher E<sub>we</sub> enhance the Li-NRR by improving the mass transport regulation between reactant species. However, these thicker and denser SEI morphologies lead to current instabilities due to dynamic SEI thickening and breakdown.