Direct Conversion of N<sub>2</sub> and Air to Nitric Acid in Gas–Water Microbubbles
Sandeep Bose, Mohammad Mofidfar, Richard N. Zare
Abstract
We report a simple, direct, and green conversion of air/N 2 to nitric acid by bubbling the gas through an aqueous solution containing 50 μM Fe 2+ ions. Air stone, along with ultrasonication, was employed to generate gas microbubbles. H 2 O 2 produced at the water–gas interface undergoes Fenton’s reaction with Fe 2+ ions to produce OH • that efficiently activates N 2, yielding nitric acid as the final product. Nitrate (NO 3 – ) formation occurs without the use of any external electric potential or radiation. The concentration of NO 3 – increased linearly with time over a period of 132 h. The average NO 3 – production rate is found to be 12.9 ± 0.05 μM h –1 . We envision that this nitrogen fixation strategy that produces nitric acid in an eco-friendly way might open the possibility for the energy-efficient and green production of nitric acid.