TiO2 Nanotubes Loaded with Au Nanoparticles as Efficient Photocatalyst for Toluene Degradation

Titanium dioxide (TiO2) is a very well-known photocatalytic material due to its photo-reactivity, high stability, non-toxicity, and easily availability. Recently, in order to enhance photocatalytic activity of the traditionally used TiO2 nanoparticles and to overcome their drawbacks (i.e. requirement of large amount of material, difficulty in catalyst recycling, aggregation into larger particles), one-dimensional nanostructured materials such as nanotubes, nanowires and nanorods have been studied. Moreover, intense efforts have been focused on the modification of nanostructured TiO2 by various strategies (e.g. metal nanoparticles deposition, doping metal ions/non-metal ions, coupling with other semiconductors) in order to alter the electronic properties by narrowing the band gap energy of this material, resulting in higher reaction rates for the photocatalytic degradation of organic pollutants.[1] With this aim, various metal nanoparticles such as Pt, Au and Ag have been employed in TiO2 nanotubes (NTs) through photo-deposition, deposition-precipitation or ion-exchange preparation methods. We present here a different synthetic protocol for the deposition of Au nanoparticles (NPs) onto ordered TiO2 nanotubes (NTs) grow on the surface of titanium foils by electrochemical anodization method.[2] Au NPs with controlled size (< 5 nm) were prepared by co-condensation of Au vapors with acetone vapors, according to metal vapor synthesis (MVS) technique.[3] They were further deposited by simple dip of the Ti foils covered by TiO2 NTs in MVS-derived Au/acetone solutions at room temperature. The role of the deposited Au amount (obtained by controlling the contact time between the support and Au/acetone solutions) on the photocatalytic efficiency of the system for toluene degradation in air was investigated. All the synthesized samples were fully characterized by SEM, TEM and STEM techniques (see Figure) pointing out the high Au NPs dispersion as well as the beneficial effect of the metal-support interactions.