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.