Titania nanotubes decorated with anatase nanocrystals as support for active and stable gold catalysts for CO oxidation

Abstract

Gold nanoparticles supported on titania nanostructured materials were prepared, characterized and tested in CO oxidation. Two nanostructured supports were used: titania nanotubes (TNT) synthesized by the Kasuga method and titania nanotubes decorated with TiO2 anatase nanocrystals prepared by post-synthetic treatment of TNT with 0.05M HNO3 solution at 70°C for 48h (TNT-T). Gold catalysts with 4wt.% of Au nominal loading were prepared by deposition-precipitation with urea. A reference Au catalyst supported on TiO2 Degussa P-25 was also prepared. Supports and catalysts were characterized by N2 physisorption, XRD, UV–vis and Raman spectroscopy, TPR, SEM-EDX and HRTEM. HRTEM characterization showed that gold nanoparticles with an average size between 2 and 7nm were obtained in all catalysts making them suitable for CO oxidation. Catalytic tests showed differences in activity and stability among the prepared catalysts. The Au/TNT catalyst presented poor activity for CO oxidation, meanwhile the Au/TNT-T catalyst showed higher activity than the Au/TiO2 Degussa P-25, especially at a low temperature interval (−10 to 100°C). Stability tests performed for Au/TNT-T and Au/TiO2 Degussa P-25 catalysts at 25°C revealed higher stability of the Au/TNT-T catalyst, attributed to low sintering of gold nanoparticles.