Search results for "cerium"

Influence of the preparation method on the activity of ceria zirconia mixed oxides for naphthalene total oxidation

2013

Cerium/zirconium mixed oxides, with different Ce/Zr ratios, have been synthesised by a co-precipitation method using two different precipitating agents (sodium carbonate and urea) and tested for the total oxidation of naphthalene. Catalysts were characterized by N2 adsorption, XRD, Raman, TPR, XPS and DRIFTS. Ceria prepared by carbonate precipitation had low activity and this is likely to be related to the high concentration of residual surface carbonate that covers catalytic sites and inhibits reaction. For carbonate precipitation, increasing the Zr content to 1% resulted in a significant increase of activity, which is related to the decrease of surface carbonate. Increasing the Zr content…

CCDC 1510395: Experimental Crystal Structure Determination

2017

Related Article: Maria Vanda Marinho, Daniella O. Reis, Willian X. C. Oliveira, Lippy F. Marques, Humberto O. Stumpf, Mariadel Déniz, Jorge Pasán, Catalina Ruiz-Pérez, Joan Cano, Francesc Lloret, and Miguel Julve|2017|Inorg.Chem.|56|2108|doi:10.1021/acs.inorgchem.6b02774

Cation Diffusion and Segregation at the Interface between Samarium-Doped Ceria and LSCF or LSFCu Cathodes Investigated with X-ray Microspectroscopy

2017

The chemical compatibility between electrolytes and electrodes is an extremely important aspect governing the overall impedance of solid-oxide cells. Because these devices work at elevated temperatures, they are especially prone to cation interdiffusion between the cell components, possibly resulting in secondary insulating phases. In this work, we applied X-ray microspectroscopy to study the interface between a samarium-doped ceria (SDC) electrolyte and lanthanum ferrite cathodes (La0.4Sr0.6Fe0.8Cu0.2O3(LSFCu); La0.9Sr0.1Fe0.85Co0.15O3(LSCF)), at a submicrometric level. This technique allows to combine the information about the diffusion profiles of cations on the scale of several micromet…

1D cerium oxy-hydroxide nanostructures deposition via electrogeneration of base into anodic alumina membrane

2008

Antioxidant activity of cerium dioxide nanoparticles and nanorods in scavenging hydroxyl radicals

2019

Cerium oxide nanoparticles (CeNPs) have been shown to exhibit antioxidant capabilities, but their efficiency in scavenging reactive oxygen species (ROS) and the underlying mechanisms are not yet well understood. In this study, cerium dioxide nanoparticles (CeNPs) and nanorods (CeNRs) were found to exhibit much stronger scavenging activity than ·OH generation in phosphate buffered saline (PBS) and surrogate lung fluid (SLF). The larger surface area and higher defect density of CeNRs may lead to higher ·OH scavenging activity than for CeNPs. These insights are important to understand the redox activity of cerium nanomaterials and provide clues to the role of CeNPs in biological and environmen…

Synthesis and Structural Study of Tetravalent (Zr 4+ , Hf 4+ , Ce 4+ , Th 4+ , U 4+ ) Metal Complexes with Cyclic Hydroxamic Acids

2015

Six- and seven-membered cyclic hydroxamic acids, such as 1-hydroxypiperidine-2-one (1H, 1,2-PIPOH) and 1-hydroxyazepan-2-one (2H), have recently been identified in some mixed siderophores as one of their three chelating subunits. Compared to their ubiquitous noncyclic counterparts, cyclic hydroxamates are preorganized for metal binding. Surprisingly, the coordination chemistry of these bidentate, monoanionic ligands remains virtually unknown, even in the case of iron(III). We report herein the first structural study of the complexes of 1– and of 6–, an unsaturated seven-membered ring analog of 2–, with tetravalent cations of transition metals (zirconium and hafnium), lanthanide (cerium), an…

Metal Oxide/Polymer Hybrid Nanoparticles with Versatile Functionality Prepared by Controlled Surface Crystallization

2012

Metal oxide/polymer hybrids are prepared from polystyrene nanoparticles functionalized at the surface with phosphonate and phosphate groups. The polymer particles are synthesized with specifically designed surface-active monomers (surfmers) and used as nucleation surfaces for the controlled in situ crystallization of cerium, iron, and zinc oxide nanocrystals. The formation of the metal oxide is driven by the addition of a base to suspensions of the polymer particles containing the corresponding precursor. The crystal formation at the particle surface is studied for the different hybrid systems by X-ray diffraction and transmission electron microscopy (TEM). The potential catalytic activity …

Synthesis of high-surface area CeO2 through silica xerogel template: influence of cerium salt precursor”;

2010

Abstract Ceria nanosized oxides with high surface area were synthesized by means of a templating approach, using a porous silica xerogel with surface area as high as 718 m2/g. After impregnation of the silica template with the cerium salt solution and further calcination at 600 °C, the final ceria oxide was recovered by dissolving the silica framework in NaOH solution. The effect of cerium counteranion, nitrate or chloride, on the textural and reduction properties of the ceria oxide was examined. Characterizations by BET and pore size distribution, XRD, TPR and SEM/EDX techniques were performed. The silica xerogel templated approach resulted in the preparation of ceria with surface area of …

Magnetically enhanced polymer-supported ceria nanocatalysts for the hydration of nitriles.

2020

The heterogeneous catalysis of the hydration of nitriles to amides is a process of great industrial relevance in which cerium(IV) oxide (also referred to as ceria) has shown an outstanding catalytic performance. The use of non-supported ceria nanoparticles is related to difficulties in the purification of the product and the recovery and recyclability of the catalyst. Therefore, in this work, ceria nanoparticles are supported on a polymer matrix either by synthesizing polymer particles by so-called Pickering miniemulsions while using ceria nanoparticles as emulsion stabilizers or, as a comparison, by in-situ crystallization on preformed polymer particles. The former strategy presents signif…

<title>Cerium-containing counter electrodes for transparent electrochromic devices</title>

1997

Films of Me-Ce oxide (Me: Ti, Zr, Sn, W) and of Ni-Ce hydroxide were produced by reactive magnetron co-sputtering. Li intercalation in Me-Ce oxide, and H exchange in Ni-Ce hydroxide, were accomplished electrochemically. Electrochromism was quenched in proportion with the Ce content in Me-Ce oxide. Films of Zr-Ce (and to some extent Ti-Ce) oxide were able to serve as fully transparent counter electrodes, of much interest for transparent electrochromic devices. In Ni-Ce hydroxide, the Ce addition enhanced the capacity for charge exchange.