Synergistically activating N2 and CO2 at water microdroplet interfaces

Nitrogen (N2), one of the most stable molecules, can be fixed naturally by lightning. However, industrial nitrogen fixation via the Haber–Bosch and Ostwald processes is energy-intensive and exacerbates carbon dioxide (CO2) emissions. Meanwhile, CO2 has reached alarming atmospheric concentrations, rendering its efficient utilization a critical scientific challenge. Herein, we demonstrate that microdroplets generated by a sonic-spray array reactor can generate surface charges without an external electric field, enabling simultaneous activation of N2 and CO2 at the gas-water interfaces to form ammonium (NH4+, 84.3 µM), nitrate (NO3-, 5.7 µM) and formate (HCO2-, 16.5 µM) within 45 minutes. The activation processes of N2 and CO2 exhibits a synergistic enhancement effect at microdroplet interfaces. Mechanistic investigation reveals novel pathways involving the CO2-facilitated N2 activation and the oxygen radical (•O)-mediated N2 activation. Overall, this research offers a sustainable and energy-efficient strategy for green nitrogen fixation and utilizing CO2 from the atmosphere.