Titanium dioxide based hybrid materials for advanced oxidation processes

A simple and versatile sol-gel route was designed and optimized to synthesize hybrid inorganic-organic TiO2 materials with complexing organic molecules (diketones, enediols, carboxylic acids) in the form of gels, small particles or stable sols. A wide characterization of the structural, morphological, optical, electronic and photoelectrochemical properties of xerogels and thin films was carried out. The physicochemical and photoresponsive properties vary strongly depending on the organic component. Ligand-to-metal charge transfer complexes in the amorphous hybrid gels allow a direct photosensitization, a recently studied mechanism of visible light activation of TiO2. Some classes of organic ligands induce the generation of superoxide radicals and their extraordinarily stable adsorption (several months) on the surface of hybrid samples. This results in oxidative catalytic activity of the materials toward aqueous pollutants in the dark, mediated by reactive oxygen species. Moreover, a simple thermal annealing of TiO2-acetylacetonate hybrid gels produces non-stoichiometric anatase samples containing structural defects and exhibiting remarkable performances in photocatalytic hydrogen production without a metal co-catalyst.