Mesoporous Titania Thin Films-Gold Nanoparticles Composites: A Comparative Study about the Role of Synthesis Variables on the Catalytic Response

In this work, the preparation of catalysts based on spherical Au nanoparticles and mesoporous TiO₂ thin films is presented, along with a systematic analysis of the effect of different synthetic variables on the catalytic activity of the composites. The Au nanoparticles (with diameters around 5 nm) were synthesized by in situ reduction inside the porous structure of amorphous TiO₂ films with different pores sizes and pore arrangements. The effect of oxide thermal treatment, pore size, film thickness, and the amount of embedded Au nanoparticles on the catalytic activity was evaluated, using two different model reactions. The obtained results indicate that the proper selection of the oxide thermal treatment is key to obtain stable and durable composites, with a reproducible catalytic performance. Interestingly, several synthetic conditions led to equivalent catalytic activities. In particular, the film thickness and the total amount of Au particles did not significantly affect the reaction constants, indicating that the proportion of particles involved in the catalysis is low. Since the preparation of the composites involves several steps, the fact that such variables have a weak influence on the catalytic activity results very useful in ensuring an easy production of reproducible and active catalysts.