The air-water interfacial nitrogen cycle produces irrigatable-level ammonium nitrate

Area of Science:

• Green Chemistry
• Materials Science
• Environmental Science

Background:

• Traditional nitrogen fixation methods are energy-intensive and contribute to greenhouse gas emissions.
• There is a growing need for sustainable and decentralized fertilizer production methods.

Purpose of the Study:

• To develop a novel, carbon-free strategy for synthesizing ammonium nitrate (NH4NO3) from atmospheric nitrogen (N2) and water.
• To utilize microscale air-water interfaces and solar photocatalysis for efficient nitrogen fixation.

Main Methods:

• A two-step process involving nitrogen oxidation reaction (NOR) and nitrate reduction reaction (NO3RR) was employed.
• Step 1: Solar-driven photocatalytic oxidation of N2 to nitrate (NO3-) in a microbubble system.
• Step 2: Reduction of nitrate intermediates to ammonium ions (NH4+) using atomized water microdroplets over a functionalized mesh.

Main Results:

• Achieved a nitrate production rate of 500 μmol L-1 h-1.
• Synthesized a 50 mL aqueous solution containing 0.94 mM NH4NO3 and 4.42 mM HNO3 derived solely from air and water.
• Demonstrated a carbon-free, catalyst-assisted platform for nitrogen fixation.

Conclusions:

• The developed air-based strategy offers a sustainable and environmentally friendly approach to nitrogen fixation.
• This technology has potential applications in decentralized green fertilizer production, particularly for hydroponic systems.
• The integration of solar photocatalysis and microdroplet interfacial chemistry paves the way for next-generation fertilizer technologies.