Resolving the Formation Mechanism of HONO via Ammonia-Promoted Photosensitized Conversion of Monomeric NO2 on Urban Glass Surfaces

Jiangping Liu; Bai Li; Huifan Deng; Yan Yang; Wei Song; Xinming Wang; Yongming Luo; Joseph S Francisco; Lei Li; Sasho Gligorovski

doi:10.1021/jacs.3c02067

Resolving the Formation Mechanism of HONO via Ammonia-Promoted Photosensitized Conversion of Monomeric NO₂ on Urban Glass Surfaces

J Am Chem Soc. 2023 May 31;145(21):11488-11493. doi: 10.1021/jacs.3c02067. Epub 2023 May 17.

Authors

Jiangping Liu^{1

2

3

4}, Bai Li⁵, Huifan Deng^{1

2

3

6}, Yan Yang^{7

8

9}, Wei Song^{1

2

3}, Xinming Wang^{1

2

3}, Yongming Luo^{4

10}, Joseph S Francisco¹¹, Lei Li⁵, Sasho Gligorovski^{1

2

3}

Affiliations

¹ State Key Laboratory of Organic Geochemistry and Guangdong Provincial Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640, China.
² Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control, Guangzhou Institute of Geochemistry, Chinese Academy of Science, Guangzhou, 510640, China.
³ Chinese Academy of Science, Center for Excellence in Deep Earth Science, Guangzhou, 510640, China.
⁴ Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500, China.
⁵ Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen, 518055, China.
⁶ University of Chinese Academy of Sciences, Beijing, 100049, China.
⁷ School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou, 510006, China.
⁸ Jieyang Branch of Chemistry and Chemical Engineering Guangdong Laboratory (Rongjiang Laboratory), Jieyang, 515200, China.
⁹ Synergy Innovation Institute of GDUT, Shantou, 515041, China.
¹⁰ Faculty of Chemical Engineering, Kunming University of Science and Technology, Kunming, 650500, China.
¹¹ Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States.

PMID: 37196053
DOI: 10.1021/jacs.3c02067

Abstract

Understanding the formation processes of nitrous acid (HONO) is crucial due to its role as a primary source of hydroxyl radicals (OH) in the urban atmosphere and its involvement in haze events. In this study, we propose a new pathway for HONO formation via the UVA-light-promoted photosensitized conversion of nitrogen dioxide (NO₂) in the presence of ammonia (NH₃) and polycyclic aromatic hydrocarbons (PAHs, common compounds in urban grime). This new mechanism differs from the traditional mechanism, as it does not require the formation of the NO₂ dimer. Instead, the enhanced electronic interaction between the UVA-light excited triplet state of PAHs and NO₂-H₂O/NO₂-NH₃-H₂O significantly reduces the energy barrier and facilitates the exothermic formation of HONO from monomeric NO₂. Furthermore, the performed experiments confirmed our theoretical findings and revealed that the synergistic effect from light-excited PAHs and NH₃ boosts the HONO formation with determined HONO fluxes of 3.6 × 10¹⁰ molecules cm^-2 s^-1 at 60% relative humidity (RH) higher than any previously reported HONO fluxes. Intriguingly, light-induced NO₂ to HONO conversion yield on authentic urban grime in presence of NH₃ is unprecedented 130% at 60% RH due to the role of NH₃ acting as a hydrogen carrier, facilitating the transfer of hydrogen from H₂O to NO₂. These results show that NH₃-assisted UVA-light-induced NO₂ to HONO conversion on urban surfaces can be a dominant source of HONO in the metropolitan area.