Surface chemistry and the nature of the adsorbed NO x species on a Pt/CeO 2 −ZrO 2 /Al 2 O 3 catalyst were investigated by IR spectroscopy, X-ray diffraction, H 2temperature programmed reduction, and NO x-temperature programmed desorption. Parallel studies were also carried out with benchmark samples such as CeO 2 /Al 2 O 3 , ZrO 2 /Al 2 O 3 , CeO 2 −ZrO 2 /Al 2 O 3 and Pt-supported versions of these materials. All samples were studied in their reduced and nonreduced forms. The use of CO as a probe molecule revealed that during the synthesis of the mixed-metal oxide systems, deposited zirconia preferentially interacted with the alumina hydroxyls, while deposited ceria was preferentially located at the Lewis acid sites. Despite the limited extent of Zr 4+ ions incorporated into the CeO 2 lattice, the reduction of ceria was promoted and occurred at lower temperatures in the presence of zirconia. When deposited on ZrO 2 /Al 2 O 3 , platinum formed relatively big particles and existed in metallic state even in the nonreduced samples. The presence of ceria hindered platinum reduction during calcination and yielded a high platinum dispersion. Subsequent reduction with H 2 led to the production of metallic Pt particles. Consequently, NO adsorption on nonreduced Pt-containing materials was negligible but was enhanced on the reduced samples because of Pt 0-promoted NO disproportionation. The nature of the nitrogen-oxo species produced after NO and O 2 coadsorption on different samples was similar. Despite the high thermal stability of the NO x adsorbed species on the ceria and zirconia adsorption sites, the NO x reduction in the presence of H 2 was much more facile over Pt/CeO 2 −ZrO 2 /Al 2 O 3. Thus, the main differences in the NO x reduction functionalities of the investigated materials could be related to the ability of the catalysts to activate hydrogen at relatively lower temperatures.

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