Effect of specific surface area on syngas production performance of pure ceria in high-temperature thermochemical redox cycling coupled to methane partial oxidation

Specific surface area is a key parameter determining the rates of thermochemical redox reactions in metal oxides.

Oxygen Anion Diffusion in Doped Ceria MxCe1-xO2-0.5x (M=Gd, Sm and Pr): A Molecular Dynamics Simulation Study

ABSTRACTMolecular dynamics simulations were utilized to determine the oxygen anion diffusivity in pure ceria (CeO2) and doped ceria MxCe1-xO2-0.5x(M=Gd, Sm and Pr) with varying level of dopant concentration from 5-30% (x = 0.05-0.3). Doping with Gd showed an improvement in oxygen anion diffusivity value by two order of magnitude (D = 4.67x10-8cm2/s at 1173 K) as compared to the undoped ceria (D = 1.33x10-10cm2/s at 1173 K). 10% of doping level was estimated as the optimum concentration of all the dopants at which all of the doped ceria materials showed maximum diffusivity of oxygen anion. Among the three dopants studied, Pr was observed to show maximum diffusivity of oxygen anion in the temperature range of 773-1173 K of simulations.

Facile synthesis of graphene-CeO2 nanocomposites with enhanced electrochemical properties for supercapacitors

The electrochemical properties of CeO2G nanocomposites have been increased compared to pure ceria and the results suggest that it is a promising material for supercapacitor applications.

Potential of Ceria-Based Catalysts for the Oxidation of Landfill Leachate by Heterogeneous Fenton Process

In this study, ceria and ceria-zirconia solid solutions were tested as catalyst for the treatment of landfill leachate with a Fenton-like process. The catalysts considered in this work were pure ceria and ceria-zirconia solid solutions as well as iron-doped samples. All the catalysts were extensively characterized and applied in batch Fenton-like reactions by a close batch system, the COD (chemical oxygen demand) and TOC (total organic carbon) parameters were carried out before and after the treatments in order to assay oxidative abatement. Results show a measurable improvement of the TOC and COD abatement using ceria-based catalysts in Fenton-like process and the best result was achieved for iron-doped ceria-zirconia solid solution. Our outcomes point out that heterogeneous Fenton technique could be effectively used for the treatment of landfill leachate and it is worth to be the object of further investigations.

Synthesis and Physicochemical Characterization of Nanostructured Pt/CeO2 Catalyst Used for Total Oxidation of Toluene

Nanostructured Pt/CeO2 with different loadings of platinum was successfully synthesized via redox reaction along with wet impregnation method. The catalytic performance of the synthesized nanocatalysts was evaluated for abatement of toluene from waste gas stream. The synthesized nanocatalysts were characterized using XRD, FESEM, TEM, N2 adsorption, FTIR and TPR-H2 techniques. Crystallographic analysis confirmed the formation of CeO2 as crystalline phase with average crystallite size of 10.5 nm. Morphological analysis showed that majority of the synthesized CeO2 particles were less than 100 nm with average particle size of 50.62 nm. TEM analysis illustrated that platinum particles were fairly well dispersed with an average size of 5-15 nm. Specific surface analysis revealed that the synthesized nanocatalysts had large enough surface area for catalytic oxidation of toluene. Temperature programmed reduction profiles indicated that Pt/CeO2 had more reducibility compared to pure ceria. The results of catalytic experiments showed that the synthesized catalysts had the ability to remove 99% of toluene via total oxidation. According to these results, the best loading of Pt on ceria was 0.5 wt% with higher activity compared to pure ceria.

Catalysts for Wet Air Oxidation Based on Ce-Zr-Pr-O Mixed Oxides Prepared by Soft Chemistry

Sol-gel Zr0.1Ce0.9O2 and Zr0.1(Ce0.75Pr0.25)O2 mixed oxides and coprecipitated pure ceria CeO2 displaying the fluorine type structure have been used as platinum or ruthenium catalysts’ supports for catalytic wet air oxidation (CWAO) of aqueous solution of acetic acid (78 mmol.L-1). These catalysts were prepared by conventional impregnation (5 wt-%) from platinum and ruthenium precursor salts or by exchange (~2 wt-%) in the case of ruthenium. A screening of catalysts in CWAO at 200°C under 2 MPa was performed and reveals that the best platinum catalyst is supported on pure ceria displaying large surface. For ruthenium catalysts, the highest conversion after 3 hours of reaction has been reached by the Ru/Zr-Ce-O system.

Synthesis and properties of nanocrystalline ceria powders

Nanocrystalline CeO2 powder was synthesized by a citrate-nitrate autoignition process and characterized by thermal analysis, x-ray diffraction, and impedance spectroscopy measurements. Nanocrystalline (20–40 nm) ceria powder with fluorite structure had formed in situ during the citrate-nitrate autoignition process. The powder prepared could be sintered to density more than 98% of theoretical density at 1450 °C. The nanocrystalline CeO2 exhibited an increase in conductivity in Ar and H2 than air above 600 °C, suggesting a possible electronic contribution to the conductivity at low oxygen partial pressures. Impedance measurements on the sintered samples unequivocally established the potential of this process in developing phase pure ceria compositions.

Chemical mechanical polishing of thermal oxide films using silica particles coated with ceria

Thermal oxide covered silicon wafers were polished with slurries containing either nano-sized ceria (CeO2) or newly prepared uniform colloidal silica particles coated with ceria. The polish rate of the latter was significantly higher than that of pure ceria. The experiments were carried out using different concentrations of the abrasives at pH 4 and 10. Little effect on the polishing rates was noted when the conditions of the slurries were varied, which was explained by the compensation of two opposite polishing mechanisms.