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Ceria-based nanocomposite with simultaneous proton and oxygen ion conductivity for low-temperature solid oxide fuel cells
KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
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2011 (English)In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 196, no 5, 2754-2758 p.Article in journal (Refereed) Published
Abstract [en]

The samarium doped ceria-carbonate (SDC/Na2CO3) nanocomposite systems have shown to be excellent electrolyte materials for low-temperature SOFCs, yet, the conduction mechanism is not well understood. In this study, a four-probe d.c. technique has been successfully employed to study the conduction behavior of proton and oxygen ion in SDC/Na2CO3 nanocomposite electrolyte. The results demonstrated that the SDC/Na2CO3 nanocomposite electrolyte possesses unique simultaneous proton and oxygen ion conduction property, with the proton conductivity 1-2 orders of magnitude higher than the oxygen ion conductivity in the temperature range of 200-600 degrees C, indicating the proton conduction in the nanocomposite mainly accounts for the enhanced total ionic conductivity. It is suggested that the interface in composite electrolyte supplies high conductive path for proton, while oxygen ions are probably transported by the SDC grain interiors. An empirical "Swing Model" has been proposed as a possible mechanism of superior proton conduction. (C) 2010 Elsevier B.V. All rights reserved.

Place, publisher, year, edition, pages
2011. Vol. 196, no 5, 2754-2758 p.
Keyword [en]
Nanocomposite electrolyte, Samarium doped ceria (SDC), Proton conductivity, Oxygen ion conductivity, Solid oxide fuel cells (SOFCs)
National Category
Inorganic Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-30998DOI: 10.1016/j.jpowsour.2010.11.033ISI: 000286705100042Scopus ID: 2-s2.0-78650512018OAI: oai:DiVA.org:kth-30998DiVA: diva2:405707
Funder
Swedish Research Council
Note
QC 20110323Available from: 2011-03-23 Created: 2011-03-07 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Dual-ion Conducting Nanocompoiste for Low Temperature Solid Oxide Fuel Cell
Open this publication in new window or tab >>Dual-ion Conducting Nanocompoiste for Low Temperature Solid Oxide Fuel Cell
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Solid oxide fuel cells (SOFCs) are considered as one of the most promising power generation technologies due to their high energy conversion efficiency, fuel flexibility and reduced pollution. There is a broad interest in reducing the operating temperature of SOFCs. The key issue to develop low-temperature (300~600 °C) SOFCs (LTSOFCs) is to explore new electrolyte materials. Recently, ceria-based composite electrolytes have been developed as capable alternative electrolyte for LTSOFCs. The ceria-based composite electrolyte has displayed high ionic conductivity and excellent fuel cell performance below 600 °C, which has opened up a new horizon in the LTSOFCs field. In this thesis, we are aiming at exploring nanostructured composite materials for LTSOFCs with superior properties, investigating the detailed conduction mechanism for their enhanced ionic conductivity, and extending more suitable composite system and nanostructure materials.In the first part, core-shell samarium doped ceria-carbonate nanocomposite (SDC/Na2CO3) was synthesized for the first time. The core-shell nanocomposite was composed of SDC particles smaller than 100 nm coated with amorphous Na2CO3 shell. The nanocomposite has been applied in LTSOFCs with excellent performance. A freeze dry method was used to prepare the SDC/Na2CO3 nanocomposites, aiming to further enhance its phase homogeneity. The ionic conduction behavior of the SDC/Na2CO3 nanocomposite has been studied. The results indicated that H+ conductivity in the nanocomposite is predominant over O2- conductivity with 1-2 orders of magnitude in the temperature range of 200-600 °C, indicating the proton conduction in the nanocomposite mainly accounts for the enhanced total ionic conductivity. The influence of Na2CO3 content to the proton and oxygen ion conductivity in the nanocomposite was studied as well.In the second part, both the proton and oxygen ion conduction mechanisms have been studied. It is suggested that the interface in the nanocomposite electrolyte supplies high conductive path for the proton, while oxygen ions are probably transported by the SDC grain interiors. An empirical “Swing Model” has been proposed as a possible mechanism of superior proton conduction, while oxygen ion conduction is attributed to oxygen vacancies through SDC grain in nanocomposite electrolyte.In the final part, a novel concept of non-ceria-salt-composites electrolyte, LiAlO2-carbonate composite electrolyte, has been investigated for LTSOFCs. The LiAlO2-carbonate electrolyte exhibits good conductivity and excellent fuel cell performances below 650 °C. The work not only developed a more stable composite material, but also strongly demonstrated that the high ionic conductivity is mainly related to interface effect between oxide and carbonate. As a potential candidate for nanocomposite, uniform quasi-octahedral CeO2 mesocrystals was synthesized in this thesis work as well. The CeO2 mesocrystals shows excellent thermal stability, and display potential for fuel cell applications.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. ix, 58 p.
Series
Trita-ICT/MAP AVH, ISSN 1653-7610 ; 2012:10
Keyword
Fuel cell, Nano, Composite, Conducting, Electrolyte
National Category
Materials Chemistry Nano Technology
Research subject
SRA - Energy
Identifiers
urn:nbn:se:kth:diva-95652 (URN)978-91-7501-387-9 (ISBN)
Public defence
2012-06-07, Sal C2, KTH-Electrum, Isafjordsgatan 26,, Kista, 10:00 (English)
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Note

QC 20120529

Available from: 2012-05-29 Created: 2012-05-28 Last updated: 2013-04-18Bibliographically approved

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