Resolving the amine-promoted hydrolysis mechanism of N2O5 under tropospheric conditions
Hydrolysis of N2O5 under tropospheric conditions plays a critical role in assessing the fate of O3, OH, and NOx in the atmosphere. However, its removal mechanism has not been fully understood, and little is known about the role of entropy. Herein, we propose a removal path of N2O5 on the water clusters/droplet with the existence of amine, which entails a low free-energy barrier of 4.46 and 3.76 kcal/mol on a water trimer and droplet, respectively, at room temperature. The free-energy barrier exhibits strong temperature dependence; a barrierless hydrolysis process of N2O5 at low temperature (≤150 K) is observed. By coupling constrained ab initio molecular dynamics (constrained AIMD) simulations with thermodynamic integration methods, we quantitively evaluated the entropic contributions to the free energy and compared NH3-, methylamine (MA)-, and dimethylamine (DMA)-promoted hydrolysis of N2O5 on water clusters and droplet. Our results demonstrate that methylation of NH3 stabilizes the product state and promotes hydrolysis of N2O5 by reducing the free-energy barriers. Furthermore, a quantitative analysis of the internal coordinate distribution of the reaction center and the relative position of surrounding species reveals that the significant entropic contribution primarily results from the ensemble effect of configurations observed in the AIMD simulations. Such an ensemble effect becomes more significant with more water molecules included. Lowering the temperature effectively minimizes the entropic contribution, making the hydrolysis more exothermic and barrierless. This study sheds light on the importance of the promoting effect of amines and the entropic effect on gas-phase hydrolysis reactions, which may have far-reaching implications in atmospheric chemistry.
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|Document Type||Journal Article|
|Department||Department of Materials Science and Engineering|
1.Shenzhen Key Laboratory of Micro/Nano-Porous Functional Materials,Department of Materials Science and Engineering,Southern University of Science and Technology,Shenzhen,518055,China
2.Department of Chemistry,University of Texas at Austin,Austin,TX 78712,United States
3.Institute for Computational Engineering and Sciences,University of Texas at Austin,Austin,TX 78712,United States
4.Department of Earth and Environmental Sciences,University of Pennsylvania,Philadelphia,PA 19104,United States
|First Author Affilication||Department of Materials Science and Engineering|
|First Author's First Affilication||Department of Materials Science and Engineering|
Zhou，Chuan,Li，Bai,Zhang，Jingyan,et al. Resolving the amine-promoted hydrolysis mechanism of N2O5 under tropospheric conditions[J]. Proceedings of the National Academy of Sciences of the United States of America,2022,119(39).
Zhou，Chuan,Li，Bai,Zhang，Jingyan,Henkelman，Graeme,Francisco，Joseph S.,&Li，Lei.(2022).Resolving the amine-promoted hydrolysis mechanism of N2O5 under tropospheric conditions.Proceedings of the National Academy of Sciences of the United States of America,119(39).
Zhou，Chuan,et al."Resolving the amine-promoted hydrolysis mechanism of N2O5 under tropospheric conditions".Proceedings of the National Academy of Sciences of the United States of America 119.39(2022).
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