Synthesis and characterization of wormhole-like mesoporous Ce0.6Zr0.35Y0.05O2 solid solutions

Abstract

Nanoparticles of Ce 0.6 Zr 0.35 Y 0.05 O 2 (CZY) solid solution have been prepared by the CTAB (hexadecyltrimethyl ammonium bromide), CTAB-EG (ethylene glycol) templating, and CTAB-EG-NaCl (in which the pores of the precursor synthesized by the CTAB-EG method is filled by a certain amount of NaCl) method, respectively. The physical properties of these materials were characterized by means of techniques such as X-ray diffraction (XRD), high resolution scanning electron microscopy (HRSEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and N 2 adsorption-desorption measurements. The CZY samples synthesized by the above three methods display wormhole-like mesoporous morphology and cubic crystal structures. The materials are narrow in pore size distribution (averaged pore diameter = 5.3-7.1 nm), high in surface areas (95-119 m 2 /g), and large in pore volumes (0.16-0.18 cm 3 /g). It has been demonstrated that the introduction of NaCl is capable of retaining the pore structures of solid nanomaterials at high-temperature calcination.PHYSICAL CHEMISTRY Ce 0.6 Zr 0.35 Y 0.05 O 2 solid solution, templating synthesis method, wormhole-like mesoporous framework, NaCl filler, rare earth ZrO 2 can be employed as a catalyst or support because it has good isomorphism and surface centers of both acidic and basic nature. Being large in surface area, highly ordered in pore channels, and having surface structures that can be modified easily by chemical means, mesoporous zirconia is superior to its nonporous counterpart [1] in adsorption and catalytic applications. The pore structures of mesoporous zirconia, however, collapse with the removal of surfactants in high-temperature calcination. Despite such deterioration of thermal stability could be hindered through the introduction of a small amount of phosphate or sulfate ions [2] or other cations [3,4] , the added entities exert a negative influence on the catalytic activity, and the modified materials are not suitable to be used as catalysts and supports. In recent years, the ceria-zirconia solid solutions are investigated for the widening of the operation window of three-way catalysts [5] . The results show that the incorporation of a certain amount of ZrO 2 to the CeO 2 lattice can significantly enhance the oxygen storage-release (redox) ability and thermal stability. Although ceriazirconia solid solutions of high surface area have been reported in the literature, most of them were calcined at temperatures below 450℃. It is known that the higher the calcination temperature, the lower is the surface area of the as-received sample. In other words, the materials calcined at low temperatures might not be suitable for catalytic systems that operate at temperatures higher than the temperature adopted for calcination. Therefore, it is a challenge to develop a strategy for the generation of high-surface-area porous ceria-zirconia solid solutions that is applicable in high-temperature operations. The ceria-zirconia solid solutions reported so far are mos...

Recent advances in mass spectrometry based single cell analysis methods

“…同 样, Yu 等 [16] 采用热分解草酸盐的方法制备得到了比 表面积为 179 m 2 g 1 的介孔 NiO 粒子. 而 Yan 等 [17] http://engine.scichina.com/doi/10.1360/N032015-00068 [18,19] . 图 2 是 meso-Ni-1-y 系催化剂的 广角 XRD 图, 各衍射峰对应的晶面已标于图中, 与 JCPDS 中 PDF No.78-0423 标准(NiO)图一致, 属于面 心立方型晶体结构.…”