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Article Dans Une Revue Journal of Physical Chemistry C Année : 2014

Water Capillary Condensation Effect on the Photocatalytic Activity of Porous TiO2 in Air

Résumé

Spectroscopic ellipsometry was utilized to follow in situ the photodegradation of organic species at TiO2 interfaces during UV irradiation in real operating conditions. Mesoporous crystalline TiO2 thin films were used as photoactive catalyzers, while lauric acid was used as the model pollutant. After infiltration of lauric acid in the TiO2 film, the local photocatalytic activity was deduced by monitoring the variation of refractive index, which is directly related to the total organic content (TOC) elimination, during irradiation at 364 nm within different atmosphere compositions in O-2 and H2O vapor. Results revealed that the presence of both H2O (hydroxyl groups) and O-2 is critical due to their role as electron and hole scavengers when adsorbed at the surface of TiO2. The photodegradation activity speed is not constant along the test as a result of the variation in OH and H2O content into the pore. Interestingly, while the activity was not significantly influenced between 10% and 20% of O-2 and between 20% and 60% of relative humidity (P/Po), it considerably increases for relative humidity above 60%. This is attributed to the fact that above 60% humidity, water exists under liquid state in the pores as a result of the capillary condensation as shown by ellipsometry porosimetry. This reveals that a liquid water environment, obtained in nanopores at high humidity by capillary condensation, provides better conditions for heterogeneous photocatalytic activity. It also proves that the evaluation of the photocatalytic activity of a given material in water medium is not directly reliable for the quantification of its photocatalytic activity in the gas phase.

Domaines

Matériaux
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Dates et versions

hal-01289946 , version 1 (17-03-2016)

Identifiants

Citer

Ronghua Li, Marco Faustini, Cédric Boissière, David Grosso. Water Capillary Condensation Effect on the Photocatalytic Activity of Porous TiO2 in Air. Journal of Physical Chemistry C, 2014, 118 (31), pp.17710-17716. ⟨10.1021/jp5046468⟩. ⟨hal-01289946⟩
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