MTBE visible-light photocatalytic decomposition over Au/TiO2 and Au/TiO2–Al2O3 sol–gel prepared catalysts

The synthesis, characterization and photoactivity for the MTBE decomposition on Au/TiO2–Al2O3 and Au/TiO2 sol–gel synthesized photocatalysts are reported. The semiconductor supports TiO2, and TiO2–Al2O3 were prepared by gelling titanium and aluminum alkoxides, whereas gold nanoparticles were prepared by the deposition–precipitation method with urea. Reference Au-supported photocatalysts were also prepared using the incipient impregnation method. Nitrogen adsorption as well as XRD, UV–vis and STEM-EDAX spectroscopies was used to characterize the solids. A shift of the band gap to the visible region was observed in gold-supported solids. The Eg band of the supports was shifted to the lower energy region for gold-supported catalysts. UV–vis characterization showed a gold plasmon surface resonance band (∼560 nm) in catalysts showing particles >7.0 nm. It is showed that the photocatalytic decomposition of MTBE in water (500 ppm) carried out with visible-light source (λ 495 nm) strongly depend of the Au particle size (6.4–25 nm). The catalysts with gold particle size ≤7.5 nm are the most active. It is proposed that in the catalyst with gold particle <7.0 nm the Auδ+ electrodeficiency is the responsible of the highest activity. Meanwhile, in catalysts with gold particles >7.0 nm the plasmon surface resonance band plays an important role in the photoactivity behavior.

It is showed that on supported gold photocatalysts with varying gold particle size the MTBE photodegradation expressed as TOC (total organic carbon) strongly depend on the gold particle size. The photoactivity decreases as the particle size increases. Smaller gold particles <7.0 nm are the most active for this reaction under visible-light source. Figure optionsDownload as PowerPoint slide