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

This work focuses on the synthesis and photocatalytic performance of mesoporous TiO2 films containing embedded gold nanostructures. The TiO2 films were prepared by the EISA (evaporation-induced self-assembly) process and loaded with Au either by impregnation followed by reduction with NaBH4 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 TiO2 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 TiO2 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.