Catalytic behavior of gold nanoparticles supported on a TiO 2 -Al 2 O 3 mixed oxide for CO oxidation at low temperature.

The present work highlights the versatility of a TiO 2 -Al 2 O 3 mixed oxide bearing highly dispersed gold nanoparticles that was applied in the CO oxidation reaction at room temperature. The TiO 2 , Al 2 O 3 , and TiO 2 -Al 2 O 3 supports were synthesized by the sol-gel method, while gold nanoparticles were added by the deposition-precipitation with urea method using a theoretical Au loading of 2 wt.%. A promotional effect of the TiO 2 -Al 2 O 3 support on the activity of gold catalysts with respect to TiO 2 and Al 2 O 3 was observed; Au/TiO 2 -Al 2 O 3 showed outstanding CO oxidation, being active from 0 °C and stable throughout a 24-h test. As for the alumina content (5, 10, and 15 wt.%) in TiO 2 , it improved the textural properties by retarding the crystal growth and anatase-rutile phase transformation of TiO 2 , suppressing the deposition of carbon on the catalyst surface and stabilizing the Au nanoparticles even at high temperatures. Gold was highly dispersed with nanoparticle sizes ranging from 1 to 2 nm when H 2 was used to treat thermally the Au/TiO 2 -Al 2 O 3 , Au/TiO 2, and Au/Al 2 O 3 materials. In addition, the XPS technique helped elicit that Au 0 and Au 1+ boosted their interaction with the TiO 2 , Al 2 O 3 , and TiO 2 -Al 2 O 3 supports by means of charge transfer, which resulted in outstanding CO oxidation activity from 0 °C. Likewise, the key factors that control the peculiar catalytic performance in the CO oxidation reaction are discussed, which represents a step forward in the versatility behavior of gold catalysts supported on mixed oxide catalysts.