Photoelectrochemical N ₂ ‐to‐NH ₃ Fixation with Recorded Yield Rate by Steering Solid‐Electrolyte Interphase

Abstract

ABSTRACT Achieving efficiently lithium (Li)‐mediated photoelectrochemical (PEC) nitrogen (N 2 )‐to‐ammonia (NH 3 ) fixation at low overpotential under mild conditions remains a highly challenging task due to the complex and sluggish interfacial chemical processes. Here, we report a novel multifunctional electrolyte with ethyl 3,3,3‐trifluoropropionate and sodium cation (Na + ) to form a porous solid‐electrolyte interphase (SEI) with optimizing organic/inorganic composition on the photocathode surface, leading to a rapid and stable conversion cycle of Li + → Li → lithium nitride (Li 3 N). As a result, the Li‐mediated PEC N 2 reduction reaction system realizes a high NH 3 yield rate of ∼93 µg h −1 cm −2 with a high faradaic efficiency (FE) of ∼67% at 0.55 V vs. Li redox couple (vs. Li/Li + ) under 1 sun illumination. When the light intensity is increased to 2 sun, it even achieves a record‐breaking submilligram‐level NH 3 yield rate, ∼109 µg h −1 cm −2 . This work reveals a critical role of SEI for accelerating Li‐Li + cycle and provides a valuable guidance for building an efficient Li‐mediated PEC N 2 ‐to‐NH 3 fixation at ultra‐positive potential vs. Li/Li + .