Relations entre la structure et la texture poreuse de xérogels de TiO2 dopés au phosphore et leurs propriétés photocatalytiques

The sol-gel process is used to prepare phosphorus (P)-doped TiO2 xerogels by cogelation of Ti(O-iPr)4 with a functionalized P-based alkoxide : NH2-(CH2)2-NH-(CH2)2-P(O)-(OEt)2, in various alcohols. These xerogels were dried under vacuum at 150°C during 12 h, and calcined under air for 5 h at 350 °C, 450 °C, 550 °C and 650 °C. The samples obtained were characterized by X-ray diffraction, nitrogen adsorption-desorption isotherms and diffuse reflectance spectroscopy in UV/Vis region. The presence of phosphorus in the samples leads to a significant increase of their specific surface area, proportionally to the amount of phosphorus in the sample. Furthermore, the doping of the TiO2 by a phosphonate compound increases the thermal stability of the TiO2 and delays the phase transformation from amorphous to anatase. The diffuse reflectance measurements clearly show the translation of absorption peak of TiO2 towards the visible region when the content in phosphorus increases. Indeed, it is observed a degradation of the p-nitrophenol under visible light by using these P-doped TiO2 xerogels, which means that the P-doping enhances the photocatalytic activity in the visible region.