Ceria (CeO 2 ) nanotube arrays with precisely defined size and density were directly synthesized on glass and cordierite substrates using a ZnO nanorods-assisted hydrothermal method. Eliminating the procedures of template removal and film coating, the one-step synthesis approach could greatly broaden the applications for materials with tubular structures. The proper concentration of cerium nitrate precursor solution acts a vital role to adjust the instantaneous precipitation of CeO 2 and dissolution of ZnO templates. The as-prepared CeO 2 tube arrays were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and powder X-ray diffraction (XRD) techniques, which reveal a regular tubular structure with the average diameter of 500 nm and length of 3 mm. The automotive exhaust catalytic performance of CeO 2 tube arrays prepared on the cordierite was evaluated. Compared with the ceria nanoparticles film, the target CeO 2 tubes exhibit improved catalytic activities at a low start-up temperature for oxycarbide and hydrocarbon. Furthermore, the palladium-decorated CeO 2 tubes exhibit a higher catalytic activity for the degradation of oxynitride than that of palladium/ceria particles/cordierite.

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Nano-powders of NiO-CeO2 and Bi2O3-CeO2 binary compounds for a promoter in the automotive three-way catalysts were synthesized by hydrothermal method. The X-ray diffraction result showed that the average particle size was in the range of 1112 nm, which was correspondence to the high-resolution transmission electron microscopy result that the average particle size was about 12 nm. The specific surface area of the NiO-CeO2 binary compounds was in the range of 5475 m2/g. Also the average particle size of the Bi2O3-CeO2 binary compounds was in the range of 811 nm. The oxygen storage capacity of the NiO-CeO2 and Bi2O3-CeO2 binary compounds was investigated under reduction and oxidation conditions. When the Ni and Bi concentration in CeO2 was up to 30%, the OSC values reached 2465 and 2560 molO/g separately, which indicated that NiO and Bi2O3 compounded CeO2 materials have fine catalysis activity than other cations doped CeO2-based materials and appear to be very promising for practical applications such as OSC materials.