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Wednesday, December 2, 2020 | History

2 edition of catalytic and solid state study of lanthanum doped ceria found in the catalog.

catalytic and solid state study of lanthanum doped ceria

Mark Francis Wilkes

catalytic and solid state study of lanthanum doped ceria

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Published by typescript in [s.l.] .
Written in English


Edition Notes

Thesis (Ph.D.) - University of Warwick, 1999.

StatementMark Francis Wilkes.
The Physical Object
Paginationv, 392p.
Number of Pages392
ID Numbers
Open LibraryOL19461421M

Lanthanum manganite and cobaltite based cathodes Lanthanum manganites (LaMnO3), particularly strontium-doped lanthanum manganites (La1ïxSrxMnO3 - LSM), are widely used as cathode materials in SOFCs operating at high temperatures ( °C), which is . H. J. Avila-Paredes and S. Kim, “The effect of segregated transition metal ions on the grain boundary resistivity of gadolinium doped ceria: Alteration of the space charge potential”, Solid State . Strontium-doped lanthanum ferrite (LSF) materials have shown considerable promise as solid oxide fuel cell (SOFC) cathodes. When used in conjunction with an anode-supported yttria-stabilized zirconia (YSZ) electrolyte assembly, power densities of W/cm2 at C and V can be achieved. Strontium substituted lanthanum manganates(III)(IV), La{sub 1{minus}x}Sr{sub x}MnO{sub 3+{delta}} (LSM) are cathode materials for high temperature solid oxide fuel cells/SOFC. Time resolved synchrotron X-ray powder diffraction methods have been used to study the kinetics of oxidation of lanthanum strontium manganates(III, IV) in a flow of oxygen.


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catalytic and solid state study of lanthanum doped ceria by Mark Francis Wilkes Download PDF EPUB FB2

In this study of the catalytic oxidation of CO and CH4 over lanthanum doped ceria, it is demonstrated that dopant concentration is the dominant factor in the variation in catalytic properties. This composition dependency of catalytic properties is correlated with the variations in solid state Cited by: 1.

In this study of the catalytic oxidation of CO and CH4 over lanthanum doped ceria, it is demonstrated that dopant concentration is the dominant factor in the variation in catalytic properties. This composition dependency of catalytic properties is correlated with the variations in solid state and adsorption properties.

The aim of the thesis is to determine precisely which of the dopant. As part of a catalytic study, the bulk structure and surface compositions of the mixed oxides of ceria and lanthana, Ce 1−x La x O 2−x/2, have been studied over the entire range of n x=0 and x=, the system forms solid solutions with the cubic fluorite x=, it forms solid solutions with the hexagonal close-packed structure Cited by: In this study of the catalytic oxidation of CO and CH4 over lanthanum doped ceria, it is demonstrated that dopant concentration is the dominant factor in the variation in catalytic properties.

This composition dependency of catalytic properties is correlated with the variations in solid state Author: Mark Francis Wilkes. XRD of the present catalysts distinguished three structures formed over the complete range of oxide compositions: a solid solution of lanthana in ceria is formed up to a bulk lanthanum ionic fraction, x b, of about ; a mixed phase between x b of and ; and a solid solution of ceria in lanthana when x b exceeds Cited by:   XRD of the present catalysts distinguished three structures formed over the complete range of oxide compositions: a solid solution of lanthana in ceria is formed up to a bulk lanthanum ionic fraction, x b, of about ; a mixed phase between x b of and ; and a solid solution of ceria in lanthana when x b exceeds We have presented.

Catalytic results, focused on doped ruthenium perovskites, confirm that the insertion of ruthenium in the structure of the lanthanum chromite presents a real benefit for the methane steam reforming.

Andre Heel, Lanthanum doped strontium titanate - ceria anodes: deconvolution of impedance spectra and relationship with composition and. Doped ceria materials are widely studied for their application in solid oxide fuel cell devices.

In this work we report on the average and local structure evolution of La-doped ceria (Ce(1-x)La(x. The catalytic CO oxidation results revealed that nanosized ceria-lanthana (CL) solid solution exhibits superior catalytic performance and thermal stability in comparison to ceria-zirconia (CZ) solid solution.

The rationale for excellent catalytic behavior of the CL sample was elucidated from the viewpoint of structure, redox behavior, and bulk oxygen mobility.

Accordingly, in this. Doped ceria-based (GdCeO, GDC) solid electrolytes were prepared by Solid-phase synthesis method. The effect of doping bismuth oxide and samarium oxide on the phase and microstructure of.

Sub-nanometer surface chemistry and orbital hybridization in lanthanum-doped ceria nano-catalysts revealed by 3D electron microscopy. Catalytic dissolution of ceria–lanthanide mixed oxides provides environmentally friendly partitioning of lanthanides and platinum.

Journal of Solid State Chemistry(9), Dopants enhance the catalytic properties of ceria. However, conventional techniques for synthesizing doped ceria have limitations in terms of structural homogeneity, surface area, and catalytic activity of the resulting oxide.

Use of toxic and corrosive chemicals presents further challenges. Ceria−praseodymia (CP) nanocrystalline solid solutions were prepared by a coprecipitation method and calcined at various temperatures to understand the thermal effects on the physicochemical properties of the nano-oxides.

The structural and redox properties of the synthesized samples were investigated by means of X-ray diffraction (XRD), transmission electron microscopy.

The present work explores the possible issues involving the synthesis of La-doped ceria-based nanoparticles by co-precipitation; moreover demonstrates the consequence of such issues in the final system.

The stoichiometric anomaly as revealed by the X-ray diffraction (XRD) peak shift studies confirmed a massive departure from the final target composition; indicating lanthanum depletion (~30.

Previously, our group reported nickel loaded ceria- and lanthana-supported catalysts for methane decomposition that were synthesized using a solid-state citrate fusion technique.

According to the results, a maximum initial hydrogen yield of 62% and 58% and a total carbon yield of % and % were obtained using cerium- and lanthanum oxide.

Lanthanum-based perovskite-type oxides represented by LaBO3 (B = Co, Fe, Mn) have been thought to present strong limitations for practical application although they are active for catalytic removal of NO. Cerium (Ce) substitution has been extensively studied to.

The densification and grain growth of the solid state ionic conductor material CeGdO−δ (i.e. GDC10, gadolinium-doped ceria, with Gd 10 mol.%) are analysed for nanometric and fine.

Journal Article: Structural and catalytic properties of lanthanide (La, Eu, Gd) doped ceria. The lanthanum on the surface of CeO 2 could also improve the soot oxidation activity by introduction of a carbonate pathway.

Katta et al. compared zirconium-and lanthanum-doped ceria solid. The best catalytic performance with soot conversion at T 50 of °C was obtained on La Ca CoO 3 (LAC2). The Ca doped LaCoO 3 gave a better catalytic performance when compared with the classical Pt/Al 2 O 3.

This depicts that the non-noble metal based catalyst is a possible replacement for the noble metal based catalyst. came out to be nm, for Iron doped Cerianm, for Cobalt doped Cerianm and for Copper Doped Cerianm. Engineering and is in his last year from Indian Institute 3.

Conclusion The catalysts in this experiment are prepared using Sol-Gel Method. The color of different catalysts are as follows-: Ceria -: White; Iron Doped. The cathode materials investigated in this study include La 1 − x Sr x MnO 3 (LSM), LSCF (La 1 − x Sr x Co y Fe 1 − y O 3) and a two-phase particulate composite consisting of LSM +doped-lanthanum gallate (LSGM).

Symmetrical cell studies were also performed on SOFC anode materials. Electric modulus formalism was used to study relaxation processes in the ‐mol%‐La 2 O 3 ‐doped CeO 2 system between and K in the frequency range 5 to 10 7 Hz.

Two relaxation processes were observed in the isothermal studies: one at low frequencies due to long‐range migration of free oxygen vacancies (process A) and one at high frequencies due to charge reorientation.

Jaiswal, Nandini Gupta, Brijesh Kumar, Devendra and Parkash, Om Effect of addition of erbium stabilized bismuth oxide on the conductivity of lanthanum doped ceria solid electrolyte for IT-SOFCs. Journal of Alloys and Compounds, Vol. p. CrossRef; Google Scholar.

Nanostructured doped ceria is a prospective material for catalytic applications such as the construction of membranes with mixed electronic and ionic conductivity for effective syngas production. In this article, the surface properties of nanostructured ceria doped with praseodymium have been studied by X-ray photoelectron spectroscopy, secondary ion mass spectrometry, and Fourier transform.

Introduction. Perovskite-type strontium doped lanthanum cobalt ferrite, typically La Sr Co Fe O 3-δ (LSCF), is a widely applied electrocatalyst for oxygen reduction reaction (ORR) in intermediate temperature solid oxide fuel cells (SOFCs).LSCF is a mixed oxygen ionic-electronic conductor, where the cathode reaction could take place on the whole electrocatalyst surface.

Lanthanum‐doped ceria powder with a composition Ce La O was prepared by heating the oxalate solid solution (Ce La ) 2 (C 2 O 4) 3 at K in air.

As‐prepared powder was densified to 96%–97% relative density by sintering in air at K for 4 h. Here in this study, we have attempted to explore this neglected, yet highly required role of doped lanthanum cerate materials. We have adopted a simple and cost-effective synthesis approach for LaCe 1–x M x O 3+ δ and introduction of the catalytic sites by doping transition metal ions (M) in the perovskite structure, which unveiled intrinsic.

Mei Li's 14 research works with citations and 1, reads, including: Oxygen deficient Ruddlesden-Popper type lanthanum strontium cuprate doped with bismuth as cathode for solid oxide fuel cell.

The possibility to introduce cerium in the perovskite-type titanate with formula LaSrTiO3+δ (LST) was investigated. Pure-phased LaCeSrTiO3+δ (LCST) was only obtained by synthesis at high temperature in reducing (diluted hydrogen) atmosphere.

The material exhibits the same orthorhombic symmetry with Immm space group as LST and nearly the same cell. Irfana Shajahan, Hari Prasad Dasari, M.B.

Saidutta, Effect of sintering aids on sintering kinetic behavior of praseodymium doped ceria based electrolyte material for solid oxide cells, International Journal of Hydrogen Energy, /ne, ().

In this paper we use density functional theory corrected for on-site Coulomb interactions (DFT + U) to study the defects formed in the ceria () and () surfaces doped with describe consistently the defect formed with substitutional La 3 + doping at a Ce 4 + site we use DFT and DFT + U, with U = 5 eV for Ce 4f states and U = 7 eV for O 2p states.

Praseodymium‐doped ceria (CeO 2) nanopowders have been synthesized via a simple but effective carbonate‐coprecipitation method, using nitrates as the starting salts and ammonium carbonate as the precursors produced in this work are ammonium rare‐earth double carbonates, with a general formula of (NH 4) Ce 1−x Pr x (CO 3) H 2 O (0.

The formation enthalpies from the oxide end-members (ΔH f,ox) of the CeO 2 –MO (M = La, Gd, and Y) systems were determined by high temperature oxide melt drop solution calorimetry. In each system, ΔH f,ox is slightly positive over the investigated composition range with a maximum at a certain doping level.

Above that concentration, ΔH f,ox decreases rapidly and stays almost constant. Kharton et al. 6 demonstrated increased oxygen vacancy concentration, ionic conductivity, and oxygen permeability when substituting Fe for Ni in (for).Studies by Chiba et al.

7 indicate the highest conductivity (at °C) for the composition considered in this study. In addition to considering the performance effects using the aforementioned cathodes, a Sm-doped ceria interlayer. Samaria-doped ceria (SDC) electrolyte-supported solid oxide fuel cells (SOFCs) with Cu-SDC and -SDC anode composites were fabricated.

Current-voltage and impedance-spectroscopy measurements were used to characterize their performance at temperatures between and °C. Abstract. Al 2 O 3-CeO 2 sol-gel oxides were obtained at ceria loadings of 2, 5, 10, 20 and 50 wt.%, calcined at °C and characterized by N 2 physisorption, XRD, TEM, 27 Al MAS-NMR, and TPR.

All samples present high amounts of surface ceria species and bulk ceria has significant presence from 20 wt.% of ceria. The sample with 50 wt.% presents both the reduction of bulk and interfacial.

Single phase La-doped BaTiO 3 with the formula Ba 1−x La x Ti 1−x/4 O 3: 0⩽x⩽ was prepared by solid state reaction of oxide mixtures at ° C, 3 days, in O 2.

The tetragonal distortion in undoped BaTiO 3 decreased with x and samples were cubic for x⩾ Preparation of Gold–Ceria Catalysts. Preparation of ceria and doped ceria as supports for gold catalysts. Deposition of gold. Characterization of Gold–Ceria Catalysts. Dispersion and oxidation state of supported gold.

State of ceria and modified ceria supports. Structural features. WGS Catalytic Activity on Gold–Ceria Catalysts. The creation of composite cathodes is a good way to enhance the cathodic performance.

They are composed of a solid electrolyte and an electronic conducting electrocatalytic material as in the La Ca Fe Ni O 3-δ /samarium-doped ceria (SDC) symmetrical cells reported in a previous work.

Designing better cathode materials for solid oxide fuel cells can be aided by quantum‐chemical calculations on oxygen reduction on Sr‐doped LaMnO 3 surfaces (La Sr MnO 3 =LSM), which show that the reaction (see energy profile [eV]) proceeds via superoxo‐ (La‐super and Mn‐super) and peroxo‐like (Mn‐per) intermediates, dissociation and incorporation into the bulk (La.Methane dry reforming (MDR) allows the transformation of carbon dioxide and methane, the two main greenhouse gases, into syngas.

Given the high endothermicity of the process, it is necessary to produce a catalytic system that is very active, selective and resistant to coking deactivation; this work focuses on the development of a heterogeneous catalyst based on nickel supported on cerium oxide.1.

Introduction Ceria–zirconia (Ce 1−x Zr x O 2) solid solutions exhibit superior performance as heterogeneous catalytic materials due to its good thermal stability, 1,2 excellent oxygen storage/release capacity and reducibility.

3–5 In the last few decades, Ce 1−x Zr x O 2 has been extensively used as an active component in three-way catalysts (TWCs) to expand the air-to-fuel ratio.