Synergistically Activating N2 and CO2 at Water Microdroplet Interfaces.

Nitrogen (N2) fixation is essential for sustaining life but is challenging under ambient conditions. Industrial N2 fixation is energy-intensive and exacerbates carbon dioxide (CO2) emissions, while high concentration of atmospheric CO2 urgently requires scalable mitigation strategies. In this study, we report that simultaneous spontaneous activation of N2 and CO2 under ambient conditions in microdroplets, producing ammonium (NH4 +), nitrite (NO2 -), and formate (HCO2 -), as confirmed by isotopic labelling experiments and theoretical calculations. This can clarify the doubts about environmental ammonia pollution in microdroplets. The activation of N2 and CO2 exhibits a synergistic enhancement effect in microdroplets. Mechanistic investigation reveals novel pathways involving the CO2-facilitated N2 fixation and the oxygen radical (•O)-mediated N2 fixation. This discovery offers a sustainable pathway for green N2 fixation and atmospheric CO2 utilization, and offers insights into the potential formation pathway of HONO in the atmosphere.