Hydrothermal preparation and photocatalytic activity of mesoporous Au-TiO2 nanocomposite microspheres.

Au-TiO2 nanocomposite microspheres were prepared by hydrothermal treatment of precipitates of tetrabutyl titanate (Ti(OC4H9)4) in a mixed solution of water, ethanol and Au colloid particles at 180 degrees C for 7 h. The as-prepared products were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, nitrogen sorption, UV-visible diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy and photoluminescence spectroscopy. The photocatalytic activity was evaluated by photocatalytic oxidation decomposition of formaldehyde in air. The results showed that the presence of nanosized Au particles slightly depressed the grain growth of anatase, resulting in smaller crystallite size and greater specific surface areas. Moreover, the absorbance and photoluminescence of anatase TiO2 was modified by those added Au nanoparticles and an appropriate Au amount in Au-TiO2 nanocomposite microspheres led to increase of band gap, decrease of photoluminescence intensity and prolongation of life of photo-generated electrons and holes. The photocatalytic activity of Au-TiO2 nanocomposite microspheres was obviously higher than that of pure TiO2 microspheres and Degussa P25. When the atomic percentage ratio of Au to Ti was below 0.00425, the apparent reaction rate constants increased. When the atomic percentage ratio of Au to Ti reached 0.00425, the sample displayed the highest photocatalytic activity.