Photoelectrochemical N₂-to-NH₃ Fixation with Recorded Yield Rate by Steering Solid-Electrolyte Interphase

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Efficient nitrogen (N₂) to ammonia (NH₃) fixation under ambient conditions is crucial for sustainable agriculture and chemical synthesis.
• Current methods often require high energy input or suffer from low efficiency due to complex interfacial processes.

Purpose of the Study:

• To develop a novel multifunctional electrolyte for enhanced lithium (Li)-mediated photoelectrochemical (PEC) nitrogen fixation.
• To optimize the solid-electrolyte interphase (SEI) for efficient Li⁺/Li conversion and N₂ reduction.

Main Methods:

• Design and synthesis of a novel electrolyte containing ethyl 3,3,3-trifluoropropionate and sodium cations (Na⁺).
• Formation of a porous SEI layer on the photocathode surface with optimized organic/inorganic composition.
• Investigation of the Li⁺ → Li → lithium nitride (Li₃N) conversion cycle under photoelectrochemical conditions.

Main Results:

• Achieved a high NH₃ yield rate of ~93 µg h^-1 cm^-2 with a Faradaic efficiency (FE) of ~67% at 0.55 V vs. Li/Li⁺ under 1 sun illumination.
• Demonstrated a record-breaking NH₃ yield rate of ~109 µg h^-1 cm^-2 at 2 sun illumination.
• The novel SEI layer significantly accelerated the Li-Li⁺ cycle, enabling efficient N₂ reduction.

Conclusions:

• The developed multifunctional electrolyte and optimized SEI are critical for efficient Li-mediated PEC N₂-to-NH₃ fixation.
• This study provides a valuable strategy for designing advanced systems for ammonia synthesis at ultra-positive potentials.
• The findings pave the way for more sustainable and energy-efficient ammonia production methods.