Oxygen Permeation in Thin, Dense Ce0.9Gd0.1O1.95-δ Membranes II. Experimental Determination

Chatzichristodoulou, Christodoulos; Søgaard, Martin; Glasscock, Julie; Kaiser, Andreas; Foghmoes, Søren Preben Vagn; Hendriksen, Peter Vang

doi:10.1149/1.3559189

Cited by 30 publications

(34 citation statements)

References 34 publications

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“…• C, 9 which is promising for applications provided that sufficient lifetime can be achieved. However, the ambipolar conductivity of ceria is relatively low when only mildly reducing conditions are imposed because of the low electronic conductivity under these conditions (<1 × 10 −3 Scm −1 at 900 • C in air 10 ).…”

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confidence: 99%

Ionic/Electronic Conductivity, Thermal/Chemical Expansion and Oxygen Permeation in Pr and Gd Co-Doped Ceria Pr_xGd_0.1Ce_0.9-xO_1.95-δ

Cheng

Chatzichristodoulou

Søgaard

et al. 2017

J. Electrochem. Soc.

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The oxygen permeation flux of Ce 0.9 Gd 0.1 O 1.95-δ (CGO)-based oxygen transport membranes under oxidizing conditions is limited by the electronic conductivity of the material. This work aims to enhance the bulk ambipolar conductivity of CGO by partial substitution of Ce with the redox active element Pr. A series of compositions of Pr x Gd 0.1 Ce 0.9-x O 1.95-δ (x = 0, 0.02, 0.05, 0.08, 0.15, 0.25, 0.3 and 0.4) was prepared by solid state reaction. X-ray powder diffraction (XPD) indicates that Pr is completely dissolved in the fluorite structure up to 40 at.%. Pronounced nonlinear thermal expansion behavior was observed as a function of temperature, due to the simultaneous contributions of both thermal and chemical expansion. The electronic and ionic conductivities were measured as a function of temperature and oxygen partial pressure. Within the range from 10 to 15 at.% Pr, a drastic drop of the activation energy of the hole mobility and an abrupt increase of the hole conductivity at low temperature was observed. The behavior could be rationalized by a simple percolation model. Oxygen permeation fluxes through disk shaped samples fed with air on one side and N 2 on the other side were also measured. The oxygen flux through Pr 0.05 Gd 0.1 Ce 0.85 O 1.95-δ was higher than that for CGO by one order of magnitude owing to the enhanced electronic conductivity albeit the flux is still limited by the electronic conductivity. In terms of the electronic and ionic conductivity, the estimated maximum oxygen permeation flux of a 10 μm Pr 0.4 Gd 0.1 Ce 0.9 O 1.95-δ -based membrane exceeds 10 Nml cm −2 min −1 at 900 • C under a small oxygen potential gradient (0.21/10 −3 bar) which is promising for use in oxygen production and in oxy-fuel combustion. Also the material may be well applicable to SOFC/SOEC composite electrodes where mixed conductivity is also desirable. Dense ceramic oxygen transport membranes (OTMs) could potentially be applied for production of high purity oxygen for medical purposes, supply of oxygen in the steel industry, oxy-fuel combustion schemes, as well as in the cement and glass industries. Also, importantly, OTMs can beneficially be integrated with a biomass gasifier, allowing production of syngas (CO and H 2 ), which is a precursor for a variety of high value chemicals. 1 Besides being applicable for OTMs, 2 acceptor doped-ceria has been intensively studied for use in a number of other applications e.g. solid oxide fuel cells (SOFCs), 3 solid oxide electrolysis cells (SOECs) 4 and for electrocatalysis. 5 In particular, acceptor doped ceria (e.g. CGO) is interesting owing to high oxide ion conductivity (0.12 Scm −1 for Gd 0.1 Ce 0.9 O 1.95-δ at 900• C 6 ), appreciable electrocatalytic activity, high electronic conductivity under reducing conditions, and excellent chemical stability under harsh reducing and even corrosive gaseous conditions. 3,7 Kaiser et al. 8 reported that the oxygen permeation flux of a 27 μm asymmetric 10 at.% Gd-doped ceria-based membrane exceeds 10 ml cm −2 min −1 under a gradie...

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Ionic/Electronic Conductivity, Thermal/Chemical Expansion and Oxygen Permeation in Pr and Gd Co-Doped Ceria Pr_xGd_0.1Ce_0.9-xO_1.95-δ

Cheng

Chatzichristodoulou

Søgaard

et al. 2017

J. Electrochem. Soc.

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“…26 In Part I we provide the detailed description of the model developed to account for the behavior of a planar CGO10 membrane in a plug-flow setup.…”

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confidence: 99%

Oxygen Permeation in Thin, Dense Ce0.9Gd0.1O1.95-δ Membranes I. Model Study

Chatzichristodoulou

Søgaard

Hendriksen

2011

J. Electrochem. Soc.

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A model of a supported planar Ce 0.9 Gd 0.1 O 1.95-d oxygen membrane in a plug-flow setup was constructed and a sensitivity analysis of its performance under varying operating conditions and membrane parameters was performed. The model takes into account the driving force losses at the catalysts at the feed and permeate side of the membrane, related to the gaseous oxygen reduction and fuel oxidation, respectively, as well as the gas conversion and gas diffusion resistances in the porous support structure at the permeate side. The temperature and oxygen activity dependence of the oxide ionic and electronic conductivity and the oxygen nonstoichiometry of Ce 0.9 Gd 0.1 O 1.95-d were described based on literature data. The performance of the membrane was characterised by the delivered oxygen flux and the membrane voltage. The dependence of the performance on the various membrane and operating parameters was analyzed by a separation of the various losses. The chemical expansion of Ce 0.9 Gd 0.1 O 1.95-d under operation was estimated from the calculated oxygen activity and nonstoichiometry profiles inside the membrane.

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“…The results suggest that DPM with a lower oxygen permeation flux exhibits a higher activation energy. The decrease of oxygen flux and the increase of activation energy of DPM should be related to the limitation of electronic conductivity in CGO [30].…”

Section: Temperature Dependence Of Oxygen Permeationmentioning

confidence: 97%

Oxygen permeability and CO2-tolerance of Ce0.9Gd0.1O2−δ – SrCo0.8Fe0.1Nb0.1O3−δ dual-phase membrane

Zhou

Tang

et al. 2015

Journal of Alloys and Compounds

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Oxygen Permeation in Thin, Dense Ce_0.9Gd_0.1O_1.95-δ Membranes II. Experimental Determination

Cited by 30 publications

References 34 publications

Ionic/Electronic Conductivity, Thermal/Chemical Expansion and Oxygen Permeation in Pr and Gd Co-Doped Ceria Pr_xGd_0.1Ce_0.9-xO_1.95-δ

Ionic/Electronic Conductivity, Thermal/Chemical Expansion and Oxygen Permeation in Pr and Gd Co-Doped Ceria Pr_xGd_0.1Ce_0.9-xO_1.95-δ

Oxygen Permeation in Thin, Dense Ce0.9Gd0.1O1.95-δ Membranes I. Model Study

Oxygen permeability and CO2-tolerance of Ce0.9Gd0.1O2−δ – SrCo0.8Fe0.1Nb0.1O3−δ dual-phase membrane

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Oxygen Permeation in Thin, Dense Ce0.9Gd0.1O1.95-δ Membranes II. Experimental Determination

Cited by 30 publications

References 34 publications

Ionic/Electronic Conductivity, Thermal/Chemical Expansion and Oxygen Permeation in Pr and Gd Co-Doped Ceria PrxGd0.1Ce0.9-xO1.95-δ

Ionic/Electronic Conductivity, Thermal/Chemical Expansion and Oxygen Permeation in Pr and Gd Co-Doped Ceria PrxGd0.1Ce0.9-xO1.95-δ

Oxygen Permeation in Thin, Dense Ce0.9Gd0.1O1.95-δ Membranes I. Model Study

Oxygen permeability and CO2-tolerance of Ce0.9Gd0.1O2−δ – SrCo0.8Fe0.1Nb0.1O3−δ dual-phase membrane

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Oxygen Permeation in Thin, Dense Ce_0.9Gd_0.1O_1.95-δ Membranes II. Experimental Determination

Ionic/Electronic Conductivity, Thermal/Chemical Expansion and Oxygen Permeation in Pr and Gd Co-Doped Ceria Pr_xGd_0.1Ce_0.9-xO_1.95-δ

Ionic/Electronic Conductivity, Thermal/Chemical Expansion and Oxygen Permeation in Pr and Gd Co-Doped Ceria Pr_xGd_0.1Ce_0.9-xO_1.95-δ