Silica-Driven CO<sub>2</sub> Reduction in Water Microdroplets
Wanting Chen, Jia Liu, Qi Jiang, Ning Wang, Xuemei Wu, Deming Xia, Gaohong He, Joseph S. Francisco
Abstract
Carbon dioxide (CO 2 ), 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 CO 2 reduction pathway in ubiquitous water microdroplets, enabling the efficient conversion of CO 2 primarily into formic acid, along with other C 1 and C 2 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 (H 2 O ·– ) reduces CO 2 to a CO 2 ·– radical anion, which subsequently abstracts a hydrogen atom from Si–OH sites on SiO 2 nanoparticles, yielding HCOO – as the primary product. Simultaneously, SiO 2 nanoparticles undergo partial disintegration, exposing fresh surfaces and generating additional Si–OH sites, thereby continuously promoting CO 2 conversion. These findings provide critical insights into climate evolution mechanisms, the chemical processes underlying acid rain and aerosol formation, and the advancement of efficient CO 2 utilization strategies.