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Diesel exhaust has recently become a severe problem, and diesel oxidation catalyst (DOC) installed in the diesel exhaust treatment system is used to reduce automobile pollution containing CO, hydrocarbons (HC), and NO. In this work, for the purpose of elucidating the effect of ceria addition on the catalytic performance of Pt-based DOC in CO, HC, and NO oxidation reactions, a range of catalysts were prepared by impregnation method. Among them, the Pt/ 15CeSA catalyst showed excellent catalytic activity, and its NO maximum conversion could reach 62%. The experimental results of X-ray photoelectron spectroscopy (XPS) and highresolution transmission electron microscopy (HRTEM) confirmed that the interface Pt−O−Ce−O−Al existed in the Pt/15CeSA catalyst. Besides, more oxygen vacancies were created at this interface, which were confirmed by oxygen temperature-programmed desorption (O 2 -TPD) and Raman spectroscopic experiments, resulting in an outstanding catalytic performance of Pt/15CeSA. It is expected our research findings will be applied to other oxidation reactions.

The hydrothermal stability of NO oxidation is the key to the practical application of diesel oxidation catalysts in diesel engines, which in the laboratory requires that NO activity does not decrease after aging for 10 h with 10% H 2 O/air at 800 °C. On the one hand, the construction of a metal/oxide interface can lead to abundant oxygen vacancies (O v ), which compensate for the loss of activity caused by the aggregation of Pt particles after aging. On the other hand, YMn 2 O 5 (YMO) has excellent thermal stability and NO oxidation capacity. Therefore, a Pt/YMn 2 O 5 -La-Al 2 O 3 (Pt/ YMO-LA) catalyst was prepared by the impregnation method. The support of the catalyst, YMn 2 O 5 -La-Al 2 O 3 (YMO-LA), was obtained by mixing high specific surface LA and YMO ball-milling. Under laboratory-simulated diesel exhaust flow, the NO oxidation performance of Pt/YMO-LA did not decrease after hydrothermal aging. Combining high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and oxygen temperature-programmed desorption (O 2 -TPD), the Pt/YMn 2 O 5 interface was formed after hydrothermal aging, and the increased O v can provide reactive oxygen to Pt and YMO. The cooperative catalysis of multiple active centers composed of Pt, YMO, and O v is the crucial factor to maintain the NO oxidation performance. In addition, in situ diffuse reflectance infrared Fourier transform spectra (DRIFTs) show that an increase in O v is beneficial to the adsorption and desorption of more nitrate and nitrite intermediates, thus achieving the hydrothermal stability of NO oxidation.

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It is a recognized view that particle size could play a significant role in catalytic performance. To obtain the nanoparticles with the different size, a series of bimetallic PtPd/SiO 2 −Al 2 O 3 catalysts subjected to hydrothermal treatment in different time were prepared and applied for NO oxidation under diesel exhaust. The experimental results confirmed that the average noble particle size was gradually increased at a different variation rate, along with aging time. An increasing of average particle size resulted in the reduction of the corresponding NO turnover frequencies (TOFs) by different degrees. Thus, a new sight on the relationship between particle size and NO catalytic activity is obtained. In the aging process, the overall trend of noble metal particles got larger along with receding NO catalytic performance, yet in a period, a few small particles presented more bridged/chelating nitrate and ionic nitrate species, further retarding its rate of loss activity.