Photoactivation of Chlorine and Its Catalytic Role in the Formation of Sulfate Aerosols

• DOI: 10.1021/jacs.3c10840
• Publication Date: 2024-01-08T07:32:05Z
• Authors: Yiqun Cao; Jiarong Liu; Qingxin Ma; Chunyan Zhang; Peng Zhang; Tianzeng Chen; Yonghong Wang; Biwu Chu; Xiuhui Zhang; Joseph S. Francisco; Hong He

We present a novel mechanism for the formation of photocatalytic oxidants in deliquescent NaCl particles, which can greatly promote the multiphase photo-oxidation of SO2 to produce sulfate. The photoexcitation of the [Cl--H3O+-O2] complex leads to the generation of Cl and OH radicals, which is the key reason for enhancing aqueous-phase oxidation and accelerating SO2 oxidation. The mass normalization rate of sulfate production from the multiphase photoreaction of SO2 on NaCl droplets could be estimated to be 0.80 × 10-4 μg·h-1 at 72% RH and 1.33 × 10-4 μg·h-1 at 81% RH, which is equivalent to the known O3 liquid-phase oxidation mechanism. Our findings highlight the significance of multiphase photo-oxidation of SO2 on NaCl particles as a non-negligible source of sulfate in coastal areas. Furthermore, this study underscores the importance of Cl- photochemistry in the atmosphere.