Nitrogen fixation using metallic lithium nanoparticles formed by electrospray deposition

Area of Science:

• Catalysis
• Materials Science
• Electrochemistry

Background:

• Ambient nitrogen (N2) reduction is crucial for synthesizing nitrogenous compounds.
• Traditional ammonia synthesis methods are energy-intensive.
• Developing efficient and sustainable nitrogen fixation pathways is a global priority.

Purpose of the Study:

• To investigate the multiphase reduction of dinitrogen (N2) in aqueous microdroplets.
• To explore the formation of ammonia (NH3) and lithium nanoparticles.
• To understand the role of electric fields and interfaces in catalytic reactions.

Main Methods:

• Deposition of charged or uncharged aqueous microdroplets containing lithium salt pre-catalyst.
• Utilizing conducting or inert surfaces for droplet deposition.
• Characterization of mixed lithium nanoparticles using (S)TEM, EDS, and EELS.
• Quantification of ammonia production via mass spectrometry.

Main Results:

• Successful synthesis of ammonia (NH3) from ambient dinitrogen (N2).
• Formation of mixed lithium nanoparticles.
• Demonstrated a complete catalytic cycle involving lithium nitride hydrolysis.
• Quantified ammonia production rate (2.97 ± 0.36 μg h⁻¹ per spray source).
• Showcased the viability of using microdroplets as electron sources and air as an N2 source.

Conclusions:

• The gas-water-solid interface facilitates efficient N2 reduction.
• This method enables moisture-sensitive chemistry in aqueous droplets.
• The synthesized ammonia can be captured as hexamethylenetetramine.
• The findings have implications for environmental, prebiotic, and synthetic chemistry.