Hybrid sol–gel porous nanocomposites as efficient photocatalytic coatings: Insights in the structure/reactivity relationships

SSCI-VIDE+CARE+DAG:CGU:IBEInternational audienceStability and photocatalytic efficiency of hybrid composite films obtained by efficient dispersion of anatase TiO2 nanoparticles in various hybrid silica matrices are investigated in order to address the structure/reactivity relationship. The photocatalytic activity is systematically monitored as a function of the chemical composition of the matrix at the molecular level, and thus the final structure of the material. The partial elimination of the organic groups brings by the organosilane precursors under UV exposure was followed by HPLC and by surface analysis (XPS, contact angle). The impact of the alkoxysilane structure on the final structure of the matrix is evaluated. In the same way, the impact of thermal and photonic pretreatments on the coating photocatalytic activity is evaluated using formic acid as model pollutant. Finally, the role of the remaining organic groups in the silica network on the structure modification and on the photocatalytic activity is investigated by varying their nature and ratio. Depolluting and self-cleaning activities of optimized coatings are studied by degrading formic acid and methylene blue in different conditions of pollutant concentration and photon flux. We interestingly show that in all cases, the presence of the organic groups in the matrix induces an increase in the photocatalytic efficiency. Finally, efficient photocatalytic flexible films are prepared and show promising photocatalytic degradation mechanism under low UV excitation, comparable to solar UV irradiation.Highlights• Composite coatings made of commercial TiO2 inserted into a hybrid silica matrix.• UV pretreatment is necessary to improve the photocatalytic efficiency.• Thermal treatment is harmful for the photocatalytic efficiency.• The coating stability is followed by HPLC and by surface analysis (XPS, contact angle).• Presence of the silica organic groups is necessary to increase the coating efficiency