A thermodynamic study on CaO-doped nonstoichiometric cerium dioxide

Garnier, John E.; Blumenthal, R. N.; Panlener, R. J.; Sharma, R. K.

doi:10.1016/0022-3697(76)90017-2

Cited by 30 publications

(17 citation statements)

References 15 publications

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“… ,,− Figure a shows the oxygen non-stoichiometry of LS_MFC 0.4 A as a function of temperature measured by continuous ( P O 2 ≥ 0.028 atm) and stepwise ( P O 2 ≤ 1.7 × 10 –3 atm) heating under the given P O 2 values. Following the van’t Hoff method, ,, the enthalpy and entropy of reduction can be correlated with temperature and P O 2 according to the following equation: R 0.25em ln false( P normalO 2 false) 1 / 2 = prefix− normalΔ red H ( δ ) T + normalΔ red S ( δ ) where R is the universal gas constant and P O 2 is equal to the oxygen partial pressure referenced to the standard gas pressure (1 atm). T is the temperature in Kelvin.…”

Section: Results and Discussionmentioning

confidence: 99%

Compositionally Complex Perovskite Oxides for Solar Thermochemical Water Splitting

Zhang

Santiago

et al. 2023

Chem. Mater.

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Solar thermochemical hydrogen (STCH) generation is a promising approach for eco-friendly H 2 production, but conventional STCH redox compounds cannot easily achieve desirable thermodynamic and kinetic properties and phase stability simultaneously due to a rather limited compositional space. Expanding from the nascent high-entropy ceramics field, this study explores a new class of compositionally complex perovskite oxides (La 0.8 Sr 0.2 )(Mn (1−x)/3 Fe (1−x)/3 Co x Al (1−x)/3 )O 3 with new non-equimolar designs for STCH. In situ X-ray photoelectron spectroscopy shows preferential redox of Co. The extent of reduction increases, but the intrinsic kinetics decreases, with increasing Co content. Consequently, (La 0.8 Sr 0.2 )(Mn 0.2 Fe 0.2 Co 0.4 Al 0.2 )O 3 achieves an optimal thermodynamic and kinetic balance. The combination of a moderate enthalpy of reduction, a high entropy of reduction, and preferable surface oxygen exchange kinetics enables a maximum H 2 production of 89.97 mmol mol oxide −1 in a short 1 h redox duration. Entropy stabilization may contribute to the phase stability during redox cycling without phase transformation, which enables STCH production for >50 cycles under harsh interrupted conditions. The underlying redox mechanism is further elucidated by a density functional theory-based parallel Monte Carlo computation approach. This study suggests a new class of non-equimolar compositionally complex ceramics for STCH and thermochemical looping.

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Section: Results and Discussionmentioning

confidence: 99%

Compositionally Complex Perovskite Oxides for Solar Thermochemical Water Splitting

Zhang

Santiago

et al. 2023

Chem. Mater.

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“…Similar curves have been measured for a variety of doped ceria. 25 " 32 A discussion of these literature results has been given elsewhere. 33 The partial free energy of formation (per mol 0 2 ) of a given nonstoichiometric ceria, AG 02 , is given by where P0 2 is the oxygen partial pressure which is in equilibrium with this ceria.…”

Section: Thermodynamic Propertiesmentioning

confidence: 95%

Ceria-Based Electrodes

Mogensen

2002

Catalysis by Ceria and Related Materials

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BackgroundThe solid oxide fuel cell (SOFC) have been under development during several decades 1 since it was discovered by Baur and Preis 2 in 1937. In order to commercialise this high temperature (600 -1000°C) fuel cell it is necessary to reduce the costs of fabrication and operation. Here ceria-based materials are of potential interest because doped ceria may help to decrease the internal electrical resistance of the SOFC by reducing the polarisation resistance in both the fuel and the air electrode. Further, the possibility of using less pre-treatment and lower water (steam) partial pressure in the natural gas feed due to lower susceptibility to coke formation on ceria containing fuel electrodes (anodes) may simplify the balance of plant of the fuel cell system, and finally it is anticipated that ceria based anodes will be less sensitive to poising from fuel impurities such as sulphur.The electrolyte in an SOFC must consist of a good ion conductor, which has essentially no electronic conductivity. Otherwise the cell will be internally shortcircuited. An often-used electrolyte material is yttria-stabilised zirconia (YSZ). The electrodes must possess good electron conductivity in order to facilitate the electrochemical reaction and to collect the current from the cell. The fuel electrode usually contains metallic nickel for this purpose. The anodic oxidation of the fuel (H 2 or CO) can only take place in the vicinity of the so-called three-phase boundary (TPB), where all reactants (oxide ions, gas molecules and electrons) are present. Thus, it is advantageous to extend the length and width of the TPB zone as much as possible. One way to do this is by making a composite of Ni and YSZ called a Ni-YSZ-cermet. Another way is to use a mixed ionic and electronic conductor, which in principle can support the electrochemical reaction all over the surface as illustrated in Fig. 15.1. Partially reduced ceria is a mixed ionic and electronic 453 Catalysis by Ceria and Related Materials Downloaded from www.worldscientific.com by UNIVERSITY OF BIRMINGHAM LIBRARY -INFORMATION SERVICES on 03/21/15. For personal use only.

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“…The study of Ca‐doped CeO 2 started as early as 1970s; however, there are still several essential issues that have not been well clarified, which deserve urgent attention. (i) In general, raw materials are solid‐state oxides or carbonates, which are mechanically mixed by ball‐milling and usually require high sintering temperatures for their large particle size 9,10 . (ii) Grain growth conditions (calcination+sintering) are usually fixed and there are only very limited studies on the grain growth dependence of the bulk density, microstructure, and conductivity property 11 .…”

Section: Introductionmentioning

confidence: 99%

Effect of Grain Growth on Densification and Conductivity of Ca‐Doped CeO₂ Electrolyte

Yan

Mori

Zou

et al. 2009

Journal of the American Ceramic Society

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Doped ceria has been pursued in the past decades as a promising electrolyte material for intermediate temperature‐solid oxide fuel cells. In this study, the effects of grain growth conditions on the densification and conductivity of CaxCe1−xO2−y (x=0.05, 0.1, and 0.2) are systematically investigated. It has been found that the densification of Ca‐doped CeO2 depends strongly upon the specific calcination and sintering pathway, based on which the processing windows for achieving high sintering density are established. It is demonstrated that Ca‐doped CeO2 show competing conductivities in the intermediate temperature region compared with rare earth‐doped CeO2. The detailed microstructures associated with various processing pathways have also been realized in terms of microdomain, superstructure, and glassy phase.

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A thermodynamic study on CaO-doped nonstoichiometric cerium dioxide

Cited by 30 publications

References 15 publications

Compositionally Complex Perovskite Oxides for Solar Thermochemical Water Splitting

Compositionally Complex Perovskite Oxides for Solar Thermochemical Water Splitting

Ceria-Based Electrodes

Effect of Grain Growth on Densification and Conductivity of Ca‐Doped CeO₂ Electrolyte

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A thermodynamic study on CaO-doped nonstoichiometric cerium dioxide

Cited by 30 publications

References 15 publications

Compositionally Complex Perovskite Oxides for Solar Thermochemical Water Splitting

Compositionally Complex Perovskite Oxides for Solar Thermochemical Water Splitting

Ceria-Based Electrodes

Effect of Grain Growth on Densification and Conductivity of Ca‐Doped CeO2 Electrolyte

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Product

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Effect of Grain Growth on Densification and Conductivity of Ca‐Doped CeO₂ Electrolyte