少量CeO2的添加对Pd/La-Al2O3密偶催化剂三效性能的影响

以La改性的Al₂O₃为载体,采用共吸附浸渍法制备了一系列不同CeO₂含量的单Pd密偶催化剂,并对其进行了表征. PdO_x和CeO₂之间的强相互作用改善了Pd⁰再氧化为PdO的能力,同时增强了反应条件下硝酸盐,亚硝酸盐和异氰酸盐在载体上的吸附. 因此适量CeO₂的添加明显改善了新鲜催化剂对HC和NO_x的催化性能,且当CeO₂添加量为2%时催化效果最佳. Pd-Ce界面上PdO_x和CeO₂间强相互作用也使得PdO_x物种在高温时仍能以小颗粒的形式分散在载体上,从而显著地提高催化剂的热稳定性. 经1100 ℃高温老化后,CeO₂ （2%-4%）的存在明显拓宽了HC和NO_x的操作窗口,这对于提高单Pd密偶催化剂在汽车尾气处理上的催化性能有重要意义.     

Nano ceria catalyzed synthesis of substituted benzimidazole,benzothiazole, and benzoxazole in aqueous media

A series of substituted benzimidazoles, benzothiazoles, and benzoxazoles was synthesized by combining 1,2-phenylenediamine, 2-aminothiophenol, or 2-aminophenol with aryl, heteroaryl, aliphatic, α,β-unsaturated aldehydes in the presence of nano ceria (CeO₂) as an efficient heterogeneous catalyst.     

Visualization of the Heterogeneity of Cerium Oxidation States in Single Pt/Ce2Zr2Ox Catalyst Particles by Nano‐XAFS

The cerium oxidation states in single catalyst particles of Pt/Ce₂Zr₂O_x (x=7 to 8) were investigated by spatially resolved nano X‐ray absorption fine structure (nano‐XAFS) using an X‐ray nanobeam. Differences in the distribution of the Ce oxidation states between Pt/Ce₂Zr₂O_x single particles of different oxygen compositions x were visualized in the obtained two‐dimensional X‐ray fluorescent (XRF) mapping images and the Ce L_III‐edge nano X‐ray absorption near‐edge structure (nano‐XANES) spectra.     

Practical applications of the chemical strain effect in ionic and mixed conductors

Abstract  The chemical strain effect in solids is the deviation from linear elasticity due to the association and dissociation of point defects. Although to date this effect has been observed and studied only in Ce_0.8Gd_0.2O_1,9, one may expect that it will be found in other ionic and mixed conductors containing a large concentration of point defects. In this work, some practical applications of materials exhibiting the chemical strain effect are discussed. Based on the example of Ce_0.8Gd_0.2O_1,9, mechanical structures built from these materials should exhibit exceptional mechanical stability and are therefore very attractive for use as components of solid oxide fuel cells (SOFC) or other devices subjected to large and frequent temperature variations. The ability of these materials to withstand large strain without accumulating large stress also makes them potentially useful as flexible elements in micro-electromechanical systems (MEMS). Graphical abstract        

规则中孔氧化铈的纳米铸型合成及作为高CO氧化活性金催化载体的应用(英文)

以有序的中孔炭材料CMK-3为模板,以硝酸铈为前体,利用纳米铸型法合成了具有规则结构的中孔氧化铈,考察了模板脱除温度对中孔氧化铈微结构的影响.热重、元素分析、X射线衍射、透射电镜和氮气物理吸附结果表明,炭模板的脱除温度可低至350℃,所得氧化铈具有二维六方规则结构,比表面积高达167 m~2/g,孔径分布集中在3～5nm.采用胶体沉积法将2-5nm的金溶胶粒子沉积到所得氧化铈表面制得了Au/CeO_2催化剂,考察了Au/CeO_2在CO氧化反应中的活性.结果表明,该催化剂的活性较常规氧化铈制备的金催化利有明显提高,这可能与载体的规则结构有关.     

Effect of La3+ and Pr3+ co-doping on structural,thermal and electrical properties of ceria ceramics as solid electrolytes for IT-SOFC applications

In the present investigation, the effect of La³⁺ and Pr³⁺ co-doping on structural, thermal and electrical properties of ceria ceramics useful as solid electrolytes in intermediate temperature solid oxide fuel cells (IT-SOFCs) has been studied. The co-doped ceria Ce_0.8Pr_0.2–xLa_xO_2-δ samples have been prepared successfully via sol-gel auto-combustion synthesis. The high dense ceramic samples have been achieved by carry out an optimized conventional sintering at 1300 °C for 4 h. The powder X-ray diffraction analysis of all the co-doped ceria ceramics revealed the single phase with cubic-fluorite structure formation. Crystallographic information has been carried out from the powder X-ray diffraction and Rietveld refinement analysis. The scanning electron microscope and energy dispersive spectroscopy analysis revealed the smaller grain size with high density in microstructure and stoichiometric elemental confirmations. Raman spectra of prepared ceramics revealed the information of phase and oxygen vacancy formation in the entire compositions. The dilatometric studies of prepared co-doped ceria ceramics revealed the moderate coefficients of thermal expansion. The electrical parameters such as total conductivities and activation energies have been studied with the help of impedance spectroscopy. Among all these co-doped ceria ceramic samples, Ce_0.80Pr_0.10La_0.10O_2−δ found to exhibit the highest value of total ionic conductivity with minimum activation energy and this makes it could be a promising electrolyte material for IT-SOFC applications.