Theoretical Study on the Mechanisms of Catalytic Hydration of Diiodine Trioxide in Marine Regions

Diiodine trioxide (I₂O₃) is one of the most common iodine oxides in the marine boundary layer (MBL). Both theoretical and experimental studies have confirmed that they can be quickly formed and are relatively stable under dry conditions. However, there is no report on the field observation of I₂O₃, which means that I₂O₃ is likely to be lost in the actual marine atmosphere. But the specific loss pathways and mechanisms are still unclear. Considering that the humidity in the marine regions is generally high and the loss of I₂O₃ will be affected by some substances in the marine atmosphere, water (H₂O, W) and iodic acid (HIO₃, IA) were selected as a catalyst to investigate the catalytic hydration mechanisms of I₂O₃ at DLPNO-CCSD(T)//ωB97X-D/aug-cc-pVTZ + aug-cc-pVTZ -PP (for iodine) level of theory. The results show that hydration of I₂O₃ presents a high energy barrier, but IA can reduce it to 3.76 kcal/mol. Therefore, in the marine atmosphere, I₂O₃ can be hydrolyzed under the catalysis of IA, and cannot directly participate in the new particle formation process.