Synergistically Activating N 2 and CO 2 at Water Microdroplet Interfaces

Abstract Nitrogen (N 2 ) fixation is essential for sustaining life but is challenging under ambient conditions. Industrial N 2 fixation is energy‐intensive and exacerbates carbon dioxide (CO 2 ) emissions, while high concentration of atmospheric CO 2 urgently requires scalable mitigation strategies. In this study, we report that simultaneous spontaneous activation of N 2 and CO 2 under ambient conditions in microdroplets, producing ammonium (NH 4 + ), nitrite (NO 2 − ), and formate (HCO 2 − ), as confirmed by isotopic labelling experiments and theoretical calculations. This can clarify the doubts about environmental ammonia pollution in microdroplets. The activation of N 2 and CO 2 exhibits a synergistic enhancement effect in microdroplets. Mechanistic investigation reveals novel pathways involving the CO 2 ‐facilitated N 2 fixation and the oxygen radical ( • O)‐mediated N 2 fixation. This discovery offers a sustainable pathway for green N 2 fixation and atmospheric CO 2 utilization, and offers insights into the potential formation pathway of HONO in the atmosphere.