Comprehensive study about the heterogeneous conversion of NH3 on nanoscale TiO2 particles: insight into the mechanism and atmospheric implications. Issue 1 (28th November 2022)

• Record Type: Journal Article
• Authors: Ma, Qingxin; Zhao, Yaqi; Zhang, Peng; Liu, Chang; Lin, Tao; Wang, Ling; Chu, Biwu; He, Hong
• Is Part Of: Environmental science. Volume 10:Issue 1(2023)
• Page Start: 241
• Page End: 250
• Publication Date: 2022-11-28
• Subjects: Environmental sciences -- Periodicals; Nanotechnology -- Periodicals; 620.505
• DOI: 10.1039/d2en00966h
• Languages: English
• ISSNs: 2051-8153

Abstract

Abstract : The heterogeneous reactions of NH3 on TiO2 were comprehensively investigated using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and a flow tube reactor. Abstract : The heterogeneous reactions of NH3 on TiO2 were comprehensively investigated using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and a flow tube reactor. The effect of SO2 and illumination on the formation of surface and gaseous products was explored. The results reveal that surface hydroxyls and H2 O play important roles in the adsorption of NH3 while adsorbed sulfur species like sulfite and sulfate can significantly promote the conversion of NH3 to NH4 + under dark conditions. The reaction mechanism under light conditions is quite different from that under dark conditions. NH3 can be directly converted into gaseous NO and NO2 and particulate nitrate on the surface of TiO2 by photooxidation. Surface sulfate formed from the photooxidation of SO2 can combine with NH3 to form ammonium sulfate, which inhibits the oxidation of NH3 and alters the production ratios of NO/NO2 . The uptake coefficients of NH3 on TiO2 are in the range of 1.5–2.5 × 10 −5 regardless of illumination while SO2 shows an inhibition effect on the initial uptake of NH3 due to competition in adsorption on surface hydroxyls. These results demonstrate that the heterogeneous reaction of NH3 on TiO2 can be a significant sink of NH3 while its transformation pathway greatly depends on the environmental factors in the atmosphere.