Au/M-TiO2 nanotube catalysts (M=Ce, Ga, Co, Y): preparation, characterization and their catalytic activity for CO oxidation

The M-modified TiO 2 nanotubes (NTs) (M = Ce, Ga, Co, Y, 2.0 wt%) were synthesized by combining sol-gel method with hydrothermal treatment, based on which gold was loaded by the deposition–precipitation approach. These catalysts were loaded with 1.5 wt% gold and calcined at 300 °C, and their catalytic performance was compared with Au/TiO 2 NTs in CO oxidation. TEM results manifested Au/M-TiO 2 NTs (M = Ce, Ga, Co, Y) had smaller gold nanoparticles than Au/TiO 2 NTs. Patterns of XPS revealed the presence of the strong interaction between gold and support in Au/M-TiO 2 NTs (M = Ce, Ga, Co, Y). Ce 4+ , Ga 3+ , Co 2+ , and Y 3+ ions were present as CeO 2 , Ga 2 O 3 , CoO, and Y 2 O 3 in Au/M-TiO 2 NTs (M = Ce, Ga, Co, Y), respectively. Based on O 2 -TPD studies, Au/M-TiO 2 NTs (M = Ce, Ga, Co, Y) provided new O 2 adsorption sites for the adsorption and activation of oxygen in CO oxidation. M (M = Ce, Ga, Co, Y) modifying performed the positive effect on CO oxidation activity and Au/Y-TiO 2 NTs showed the highest activity among these catalysts. Additionally, Au/Y-TiO 2 NTs also performed excellent high-temperature stability. It was likely that the strong interaction between gold and support created the small size of gold nanoparticles, large O 2 adsorption and plenty of defects, thereby enhancing the catalytic activity of Au/M-TiO 2 NTs (M = Ce, Ga, Co, Y).