Nanostructure and catalytic properties of gold supported on group Ⅳ oxides

摘要

The effect of the support on the HRTEM features and on the FTIR spectra of adsorbed CO at 90 and 300 K of Au/TiO_2, Au/ZrO_2 and Au/CeO_2, both oxidised and reduced, has been examined. All catalysts have been prepared by the deposition-precipitation method. The aim of this work is to obtain information on the surface structure of the three catalysts in order to explain the differences observed in the catalytic activity in the CO oxidation reaction. The size and the size distribution of the metal particles produced on Au/TiO_2 and on Au/ZrO_2 are almost the same, d ≈ 4 nm. On the contrary, the ceria supported sample exhibits Au particles that are significantly smaller, d ≈1 nm, that are difficultly detected by HRTEM. FTIR data of CO adsorbed at 90 K on the three samples, either oxidized or reduced, and the spectroscopic evolution by heating up to RT, are presented and correlated with the different catalytic performances. In addition, data concerning the CO-O_2 interaction at different temperatures will be discussed. The size of gold nanoparticles together with the size and the chemical nature of the oxidic supports are shown to be relevant in determining firstly their durability and then the chemisorption and catalytic properties.