Silica-Driven CO₂ Reduction in Water Microdroplets

Carbon dioxide (CO₂), the most notorious greenhouse gas responsible for global warming and ocean acidification, could persist in the atmosphere for 50 to 200 years, posing substantial long-term environmental challenges. However, its environmental fate remains not fully clear. This study reveals a previously unrecognized silica-driven CO₂ reduction pathway in ubiquitous water microdroplets, enabling the efficient conversion of CO₂ primarily into formic acid, along with other C₁ and C₂ products such as methanol, acetic acid, and ethanol, under ambient conditions. Notably, the reaction proceeds at a rate of 3.24 mmol g^-1 h^-1, exceeding those reported for microdroplet systems utilizing amine absorbents or metal catalysts. Bonn-Oppenheimer molecular dynamics simulations further reveal that at the gas-water interface, a hydrated electron (H₂O^·-) reduces CO₂ to a CO₂^·- radical anion, which subsequently abstracts a hydrogen atom from Si-OH sites on SiO₂ nanoparticles, yielding HCOO^- as the primary product. Simultaneously, SiO₂ nanoparticles undergo partial disintegration, exposing fresh surfaces and generating additional Si-OH sites, thereby continuously promoting CO₂ conversion. These findings provide critical insights into climate evolution mechanisms, the chemical processes underlying acid rain and aerosol formation, and the advancement of efficient CO₂ utilization strategies.