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Accueil du site > Thèmes de recherche > Atmosphère & environnement > 2.2 Interactions espèces gazeuses -surfaces > 2.2.5 Photo-catalytic self-cleaning and “de-polluting” materials : sink or source of pollutants ?

2.2.5 Photo-catalytic self-cleaning and “de-polluting” materials : sink or source of pollutants ?

Recent research work has shown that materials containing titanium dioxide (TiO2) could have a “de-polluting” effect through photocatalytic phenomena which led to the development of environmental friendly materials by adding TiO2 to ordinary building materials such as concrete, cement and glass. Although various photocatalytic materials are already on the market, very little reliable information is available, except for limited technical data, regarding their impact on air quality considering the potential formation of harmful intermediates. Within different projects, we have undertaken a systematic study on the behaviour of typical atmospheric pollutants when exposed to materials containing TiO2.

Experiments have been conducted on TiO2 coated glass using a new built and well equipped outdoor 3.4 m3 simulation chamber made of Teflon. In agreement with previous studies performed under artificial light, the results obtained show that while NO uptake on the TiO2 coated glass is enhanced under irradiation, the NO2 concentration-time profile exhibits a maximum, suggesting that it is produced from the photocatalytic oxidation of NO and then converted to nitrous and nitric acids. Interestingly, ozone was observed to be formed in a high yield during the course of the experiment. In addition, the experiments have also shown a substantial formation of nitrous acid (HONO). In combination with other experiments performed using complementary experimental systems at IRCELYON and LISA, a chemical mechanism has been proposed to explain the observed ozone profiles involving nitrate radicals (ACL110). This work has been conducted within three projects (Primequal, ANR, Life+).