Ozone Formation from Illuminated Titanium Dioxide Surfaces

摘要

Titanium dioxide, TiO2, is used in a variety of remediationnprocesses due to its favorable physical, chemical, and photocatalyticnproperties.n1–3nPossible removal of NOx by means of depollutingnsurfaces containing TiO2 has been previously reported.n4–13nOthernrecent studiesn14–17nshow that this process converts NO2 to HNO2nproducing also H2O2n18nand nitrate anionsn9,18–22nwhich are thenninvolved in a renoxification process.n23nSimilarly, the photochemistrynof adsorbed nitrate on aluminum oxide has been proven to producenNO, NO2, and N2O.n24,25nHowever, the formation of non-nitrogenncontaining products in the NOx reaction with illuminated TiO2nsurfaces has been largely unexplored.nHerein, we report the first investigation of such products fromnTiO2 coated glasses exposed to nitrogen oxides (NOx)intwonsimulation chambers using both artificial and natural illuminationnand from irradiated TiO2/KNO3 films using a coated-wall flow tubenreactor. These studies demonstrate the formation of ozone fromnTiO2 surfaces containing nitrate anions.nChamber simulation experiments are performed in two differentnchambers (i) a stainless steel Multiphase Atmospheric ExperimentanSimulation Chamber (CESAM) equipped with artificial irradiationnand (ii) a Teflon outdoor chamber (see Supporting Information fornexperimental details and Figures S1 S3). After introduction ofnsynthetic air and NO into the CESAM chamber, the concentrationsnof NO, NO2, HNO2, and O3 are monitored in the dark for 1 hnThen, the artificial illumination is turned on, and the gas mixturenis again monitored for typically 90 min.