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A series of Ir and Au-Ir supported on TiO 2 catalysts were prepared by deposition-precipitation with urea to study the activity and stability of these materials in the CO oxidation reaction. Bimetallic samples were prepared using two approaches: one by codeposition of the metal precursors and the other by sequential deposition being iridium the first to be incorporated on the support. Samples were submitted to calcination in air or reduction in hydrogen thermal treatments. Nominal gold and iridium loading were 4 wt %. Samples were characterized by EDS, H 2 -TPR, HRTEM, HAADF, and CO + O 2 adsorption followed by DRIFTS. It is shown for the first time that deposition-precipitation with urea is able to deposit Ir and Au-Ir nanoparticles on TiO 2 . Catalyst pretreatment had an important effect on the structure of the iridium phase. In calcined samples, Ir spreads over the TiO 2 mainly as a thin layer of IrO 2 particles preferentially deposited on the rutile phase of TiO 2 . In reduced samples, Ir particles were homogeneously dispersed on all of the TiO 2 crystals. It is shown that, even in the samples reduced at 300 °C, IrO 2 was present in the catalysts. Ir/TiO 2 samples prepared by deposition-precipitation with urea calcined or reduced in H 2 were not active at room temperature (light-off temperature above 250 °C). The preparation protocol in bimetallic catalysts (codeposition or sequential deposition of the metals and different pretreatments) had a strong influence on the catalytic performance of the catalysts. The most active sample was the one prepared by sequential deposition and thermally treated in hydrogen at 300 °C. An enhanced activity was observed when compared to Au/TiO 2 . Besides this synergetic effect, the bimetallic catalyst was more stable in time on stream and more stable against sintering after reaction. DRIFTS experiments showed that the interaction of Au and Ir could modify the adsorption properties of catalyst surface.

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