Improving the Photocatalytic Performance of Mesoporous Titania Films by Modification with Gold Nanostructures

This work focuses on the synthesis and photocatalytic performance of mesoporous TiO 2 films containing embedded gold nanostructures. The TiO 2 films were prepared by the EISA (evaporation-induced self-assembly) process and loaded with Au either by impregnation followed by reduction with NaBH 4 or by pulsed cathodic electrodeposition. The latter approach represents a considerably easier and faster synthetic method and results in dendritic Au nanostructures as a replica of the pore system. The as-prepared composite films were characterized by scanning and transmission electron microscopy (SEM and TEM), UV−vis spectroscopy and Kr adsorption. Photocatalytic oxidation of NO was chosen as the test reaction for elimination of air pollutants. For mesoporous TiO 2 films deposited on an ITO layer, the photonic efficiency is higher than for films prepared on glass, because the pore structures are altered. Incorporation of Au results in a significant improvement in the photonic efficiency due to the generation of Schottky barriers, which inhibit the recombination of electron−hole pairs and thereby increase the concentration of photogenerated holes at the film surface reacting with NO. Compared to the impregnated nanocomposites, mesoporous TiO 2 films with electrochemically incorporated dendritic Au nanostructures provide comparable photocatalytic activities, but their preparation is much less time-consuming and of lower cost. An additional treatment with O 2 plasma leads to further increase in the photocatalytic activity due to the higher amount of hydroxyl groups on the surface, which play a significant role in the photocatalytic oxidation of NO. Mesoporous nanocomposite films are promising in photocatalysis and self-cleaning technologies.