Several nanosized catalysts Co3O4–CeO2 with varying compositions were synthesized by a surfactant-template method and further promoted by a small amount of Pd (0.5 wt%). These catalysts exhibit uniform mesoporous structure and high surface area (>100 m2 g−1). The Co3O4 crystallites in these catalysts are encapsulated by nanosized CeO2 with only a small fraction of Co ions exposing on the surface and strongly inter- acting with CeO2. Such structure maximizes the interaction between Co3O4 and CeO2 in three dimensions, resulting in unique redox properties. The introduction of Pd prominently enhances both the reduction and oxidation performance of the catalysts, due to hydrogen or oxygen spillover. These catalysts prepared by surfactant-template method exhibit excellent oxidation performance, especially the ones promoted with Pd, which show markedly enhanced CO oxidation activity even at room temperature. Based upon the results of structural properties, redox behaviors and in situ DRIFTS study, two different reaction pathways over Co3O4–CeO2 and Pd/Co3O4–CeO2 are proposed.

The complex oxide Ba–Fe–O catalysts were prepared by sol–gel method. The XRD, DTA, NO-TPD, XPS and NSC measurements were used to characterize the structures, NOx storage property and sulfur resistance ability. It is concluded that when coadsorption of NO and O2 at 400 C, the sample calcined at 750℃ possesses high NOx storage capacity and sulfur resistance. The perovskite type BaFeO3 and BaFeO3-x phases are the active centers in the catalyst for NOx storage.

The NOx storage catalyst Pt/BaAl2O4–Al2O3 was prepared by a coprecipitation–impregnation method. For fresh sample, the barium mainly exists as the BaAl2O4 phase except for some BaCO3 phase. The BaAl2O4 phase is the primary NOx storage phase of the sample. EXAFS and TPD were used for investigating the mechanism of NOx storage. It is found that two kinds of Pt sites are likely to operate. Site 1 is responsible for NO chemisorption and site 2 for oxidizing NO to nitrates and nitrites. When NO adsorbs on the sample below 200℃, it mainly chemisorbs in the form of molecular states. Such adsorption results in an increase of the coordination magnitude of Pt–O, and a decrease of that of Pt–Pt and Pt–Cl. The coordination distance of Pt–Pt, Pt–Cl and Pt–O also increases. When the adsorption occurs above 200℃, NO can be easily oxidized by O2, and stored as nitrites or nitrates at the basic BaAl2O4. Site 2 is regenerated quickly. A high adsorption temperature is favorable for nitrate formation.

A new NOx storage-reduction electrochemical catalyst has been prepared from a polycrystalline Pt film deposited on 8 mol% Y2O3- stabilized ZrO2 (YSZ) solid electrolyte. BaO has been added onto the Pt film by impregnation method. The NOx storage capacity of Pt-BaO/ YSZ system was investigated at 350℃ and 400℃ under lean conditions. Results have shown that the electrochemical catalyst was effective for NOx storage. When nitric oxides are fully stored, the catalyst potential is high and reaches its maximum. On the other hand, when a part of NO and also NO2 desorb to the gas phase, the catalyst potential remarkably drops and finally stabilizes when no more NOx storage occurs but only the reaction of NO oxidation into NO2. Furthermore, the investigation has clearly demonstrated that the catalyst potential variation versus temperature or chemical composition is an effective indicator for in situ following the NOx storage-reduction process, i.e. the storage as well as the regeneration phase. The catalyst potential variations during NOx storage process was explained in terms of oxygen coverage modifications on the Pt.