Influence of gold particle size on the photocatalytic activity for acetone oxidation of Au/TiO(2) catalysts prepared by dc-magnetron sputtering

Abstract

Two series of Au/TiO2 materials with different gold content have been prepared by dc-magnetron sputtering on ceramic shaped pure anatase or Degussa P25 TiO2. The time of deposition was varied between 1 and 20 min in order to obtain different thickness and nanoparticle size of the gold films. For comparison samples with Au loadings in the range 0.3–0.9 wt% were prepared using the deposition–precipitation methodology. The obtained materials were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), DR-UV-Vis and atomic force and scanning electron microscopy techniques. The photocatalytic activity was checked in the photo-oxidation of acetone under both UV and visible irradiation conditions. Several factors were found to influence the photoactivity. An optimal Au content corresponding to a maximum activity is observed and attributed to the occurrence of adequate titania surface coverage and Au particle size. The support plays an important role and it was found that pristine anatase on which gold (average particle size 7.7 nm) was deposed by dc-reactive sputtering exhibits the maximum of the activity. Samples prepared by dc-sputtering were more active than samples prepared by deposition–precipitation method. Also, the photocatalysts prepared using dc-reactive sputtering showed activity under both UV and visible light irradiation, while those prepared using the deposition–precipitation technique are active only under UV light. The most likely mechanism of gold activation of titania is that upon light absorption, gold nanoparticles inject electrons into the titania conduction band.