Highly efficient production of nitrite and nitrate from air at the gas-water interface of nanobubbles

We report a simple, one-step conversion of air to nitrogen oxyanions (NO x − ), i.e., nitrate (NO 3 − ) and nitrite (NO 2 − ), at the gas-water interface (GWI) of nanobubbles (NBs). The nanobubble generator is placed inside an aqueous solution of 50 μM Fe 2+ to enhance the production of hydroxyl radicals (OH•) by initiating Fenton’s reaction at the GWI. The formation of NO x − does not require any external potential or radiation. The NO x − production rate using NBs is found to be 60.4 ± 1.21 μM hour −1 , which shows a fourfold increase in the production as compared to the same reaction performed in microbubbles (15 μM hour −1 ), which is the result from an enhanced electric field strength at the GWI. We propose that this nitrogen-fixation approach presents a promising pathway for an eco-friendly, energy-efficient, and scalable solution for NO x − -based sustainable fertilizer production.