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101.
The influence of SiO2, TiO2, and ZrO2 on the structural and redox properties of CeO2 were systematically investigated by various techniques namely, X-ray diffraction (XRD), Raman spectroscopy (RS), UV–Vis diffuse
reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HREM),
BET surface area, and thermogravimetry methods. The effect of supporting oxides on the crystal modification of ceria was also
mainly focused. The investigated oxides were obtained by soft chemical routes with ultrahigh dilute solutions and were subjected
to thermal treatments from 773 to 1073 K. The XRD results suggest that the CeO2–SiO2 sample primarily consists of nanocrystalline CeO2 on the amorphous SiO2 surface. Both crystalline CeO2 and TiO2-anatase phases were noted in the case of CeO2–TiO2 sample. Formation of cubic Ce0.75Zr0.25O2 and Ce0.6Zr0.4O2 (at 1073 K) were observed in the case of CeO2–ZrO2 sample. The cell ‘a’ parameter estimations revealed an expansion of the ceria lattice in the case of CeO2–TiO2, while a contraction is noted in the case of CeO2–ZrO2. The DRS studies suggest that the supporting oxides significantly influence the band gap energy of CeO2. Raman measurements disclose the presence of oxygen vacancies, lattice defects, and displacement of oxide ions from their
normal lattice positions in the case of CeO2–TiO2 and CeO2–ZrO2 samples. The XPS studies revealed the presence of silica, titania, and zirconia in their highest oxidation states, Si(IV),
Ti(IV), and Zr(IV) at the surface of the materials. Cerium is present in both Ce4+ and Ce3+ oxidation states. The HREM results reveal well-dispersed CeO2 nanocrystals over the amorphous SiO2 matrix in the case of CeO2–SiO2, isolated CeO2 and TiO2 (A) nanocrystals and some overlapping regions in the case of CeO2–TiO2, and nanosized CeO2 and Ce–Zr oxides in the case of CeO2–ZrO2 sample. The exact structural features of these crystals as determined by digital diffraction analysis of HREM experimental
images reveal that the CeO2 is mainly in cubic fluorite geometry. The oxygen storage capacity (OSC) as determined by thermogravimetry reveals that the
OSC of mixed oxides is more than that of pure CeO2 and the CeO2–ZrO2 exhibits highest OSC. 相似文献
102.
Shuichi Naito Shigeru Aida Toshiki Kasahara Toshihiro Miyao 《Research on Chemical Intermediates》2006,32(3):279-290
In situ infrared spectroscopy was applied to elucidate the reaction mechanism of CO hydrogenation over Pd/CeO2. Instead of direct dissociation of CO, a new reaction pathway is proposed for methane formation, involving geminal dicarbonyl
intermediates and (HCO)2(a) intermediates, which may be located on the surface of Pd covered with thin layers of reduced ceria (SMST effect). Transformation
of methane formation sites into methanol formation ones by the oxidation with water vapor formed during the CO-H2 reaction is proposed, which may be located on the Pd (111) planes adjacent to ceria support. 相似文献
103.
Jacek M. Rynkowski Tadeusz Paryjczak Andrezej Lewicki Magorzata I. Szynkowska Tomasz P. Maniecki Wojciech K. Jówiak 《Reaction Kinetics and Catalysis Letters》2000,71(1):55-64
Ru/Al2O3 and Ru/CeO2-Al2O3 samples were used as catalysts in CO2 methanation. The catalysts were characterized by temperature-programmed reduction (TPR) and X-ray diffraction. The promoting effect of ceria on the cataytic activity of the catalysts under study in CO2 methanation was observed. 相似文献
104.
《Mendeleev Communications》2023,33(1):124-126
The surfactant-free synthesis of a solid film of ceria was carried out at the air–water interface from an aqueous solution of Ce(NO3)3 and gaseous NH3 as reactants. The synthesized CeO2?x ? n H2O film consists of 2D nanocrystals with a fluorite structure. The film can form a planar coating on the surface of a solid substrate or transform into curved fragments upon drying, depending on the synthesis conditions. 相似文献
105.
S. Akrabi Z. D. Doh
evi‐Mitrovi M. Radovi M. epanovi Z. V. Popovi 《Journal of Raman spectroscopy : JRS》2009,40(6):650-655
Phonon–phonon interactions and phase stability of Gd‐doped ceria nanocrystals were examined over the temperature range 293–1100 K by Raman spectroscopy. The phonon confinement model (PCM) based on size, inhomogeneous strain and anharmonic effects was used to properly describe the anharmonic interactions in this system. The interplay between size and anharmonic effects influenced different phonon decay channels in nano grains than in larger grains. After the gradual cooling down to room temperature (RT), the Raman study revealed the phase separation in this system pointing to the phase instability of Ce0.85Gd0.15O2−δ nanocrystals after heat treatment. The concentration of extrinsic (intrinsic) oxygen vacancies was also studied by Raman spectroscopy during the heat treatment of the Ce0.85Gd0.15O2−δ nanocrystalline sample. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
106.
Origin of high oxide to nitride polishing selectivity of ceria-based slurry in the presence of picolinic acid 下载免费PDF全文
We report on the investigation of the origin of high oxide to nitride polishing selectivity of ceria-based slurry in the presence of picolinic acid.The oxide to nitride removal selectivity of the ceria slurry with picolinic acid is as high as 76.6 in the chemical mechanical polishing.By using zeta potential analyzer,particle size analyzer,horizon profilometer,thermogravimetric analysis and Fourier transform infrared spectroscopy,the pre-and the post-polished wafer surfaces as well as the pre-and the post-used ceria-based slurries are compared.Possible mechanism of high oxide to nitride selectivity with using ceria-based slurry with picolinic acid is discussed. 相似文献
107.
银基陶瓷复合电极可望在中低温固体氧化物燃料电池(SOFCs)、含碳燃料SOFCs和固体氧化物电解池(SOECs)中得到广泛应用。为优选出银基陶瓷复合电极的成分,本研究采用YSZ(钇稳定化氧化锆)电解质,先将Ag-YSZ和Ag-GDC(掺钆氧化铈)材料制备成对称电极,测试其在空气下的阻抗谱,由此判断其作为阴极的性能;发现在相同的Ag含量时, Ag-YSZ的阴极极化电阻普遍低于Ag-GDC;当Ag的质量分数为65%时, Ag-YSZ的极化电阻最低,而对于Ag-GDC, Ag的质量分数是70%。然后采用空气中极化电阻最低的Ag-YSZ和Ag-GDC作为电极制备了SOFC单电池,并采用加湿氢气燃料对电池的电化学性能进行了测试。根据电池的阻抗谱数据,将极化阻抗的数值减去上述阴极阻抗的数值可得到阳极阻抗值,其结果和电池的输出特性均表明, Ag-GDC作为阳极的性能优于Ag-YSZ,即在本实验条件下, Ag-YSZ更适合用作阴极,而Ag-GDC更适合用作阳极。本研究不仅提供了关于银基复合电极材料的有用数据,还提供了一种测试SOFC阳极极化电阻的方法。 相似文献
108.
109.
Inside Back Cover: l‐Arginine‐Triggered Self‐Assembly of CeO2 Nanosheaths on Palladium Nanoparticles in Water (Angew. Chem. Int. Ed. 14/2016) 下载免费PDF全文
110.
Maximum Noble‐Metal Efficiency in Catalytic Materials: Atomically Dispersed Surface Platinum 下载免费PDF全文
Dr. Albert Bruix Dr. Yaroslava Lykhach Dr. Iva Matolínová M. Sc. Armin Neitzel Dr. Tomáš Skála Dr. Nataliya Tsud Dr. Mykhailo Vorokhta M. Sc. Vitalii Stetsovych M. Sc. Klára Ševčíková Dr. Josef Mysliveček M. Sc. Roman Fiala M. Sc. Michal Václavů Dr. Kevin C. Prince Dr. Stéphanie Bruyère Dr. Valérie Potin Prof. Dr. Francesc Illas Prof. Dr. Vladimír Matolín Prof. Dr. Jörg Libuda Prof. Dr. Konstantin M. Neyman 《Angewandte Chemie (International ed. in English)》2014,53(39):10525-10530
Platinum is the most versatile element in catalysis, but it is rare and its high price limits large‐scale applications, for example in fuel‐cell technology. Still, conventional catalysts use only a small fraction of the Pt content, that is, those atoms located at the catalyst’s surface. To maximize the noble‐metal efficiency, the precious metal should be atomically dispersed and exclusively located within the outermost surface layer of the material. Such atomically dispersed Pt surface species can indeed be prepared with exceptionally high stability. Using DFT calculations we identify a specific structural element, a ceria “nanopocket”, which binds Pt2+ so strongly that it withstands sintering and bulk diffusion. On model catalysts we experimentally confirm the theoretically predicted stability, and on real Pt‐CeO2 nanocomposites showing high Pt efficiency in fuel‐cell catalysis we also identify these anchoring sites. 相似文献