Evaluation of photocatalytic activity of porous films by in-situ environmental ellipsometric analysis

Abstract : TiO2-based materials have been extensively studied as potential material to be used in photocatalysis. In particular crystalline mesoporous thin films exhibit increased photocatalytic activities due to their exceptionally high surface area. However the study and the optimization of the photocatalysis in such porous media is not easy to be done due to the fact that the catalytic process is highly dependent from several environmental and structural parameters. The research activities of this thesis were essentially focused on (i) the fabrication of mesoporous TiO2-based photoactive thin films with tunable composition and nanostructure and (ii) their utilization as platform for fundamental study of the photocatalytic process by ellipsometry. The mesoporous films with tunable nanostructure will be fabricated by coupling sol-gel chemistry and highly controlled liquid deposition techniques. Among modern analytical tools, 2D-GISAXS, ellipsometry and ellipso-porosimetry, SEM-FEG, HR-TEM and WAXS, were used to obtain a large set of relevant information. In the first part, a model TiO2 mesoporous film was analysed by ellipsometry for fundamental investigations of the photocatalytic process kinetics in air as function of the environmental and the organic pollutant. The information obtain by ellipsometry has allowed the proposition of photodegradation mechanisms in the studied conditions. In the second part, composite mesoporous TiO2/SiO2 films with tunable optical properties were fabricated by sol-gel chemistry. A structural study on the films porous network and composition was conducted. In-situ ellispometry was also used to study the photocatalytic activity.
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Ronghua Li. Evaluation of photocatalytic activity of porous films by in-situ environmental ellipsometric analysis. Chemical Physics [physics.chem-ph]. Université Pierre et Marie Curie - Paris VI, 2016. English. ⟨NNT : 2016PA066033⟩. ⟨tel-01359756⟩

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