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Novel ceramic fuel cell using non-ceria-based composites as electrolyte
KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
2007 (English)In: Electrochemistry communications, ISSN 1388-2481, E-ISSN 1873-1902, Vol. 9, no 12, 2863-2866 p.Article in journal (Refereed) Published
Abstract [en]

A novel concept of ceramic or solid oxide fuel cell (SOFC) based on non-ceria-salt-composites electrolyte has been investigated. The fuel cell using LiAlO2-carbonate (LiNaCO3) as electrolyte exhibits excellent performances, when we used hydrogen and air as fuel and oxidant respectively, instead of molten carbonate fuel cells (MCFCs) environment. The maximum output power density can reach 466 mW/cm(2) at 650 degrees C and the discharging current keeps constant. The ion transport mechanics of the ceramic fuel cell were discussed. In the H-2/air atmosphere, the new fuel cell function should be performed only by proton or oxygen ion conduction, which differs essentially from the MCFC function, in which the CO32- conduction dominates process.

Place, publisher, year, edition, pages
2007. Vol. 9, no 12, 2863-2866 p.
Keyword [en]
LiAlO2, carbonate, non-ceria-based composite electrolytes, fuel cells, low-temperature sofcs, conductors
Identifiers
URN: urn:nbn:se:kth:diva-17177DOI: 10.1016/j.elecom.2007.10.010ISI: 000251897100025Scopus ID: 2-s2.0-36248960545OAI: oai:DiVA.org:kth-17177DiVA: diva2:335220
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Ionic Conducting Composite as Electrolyte forLow Temperature Solid Oxide Fuel Cells
Open this publication in new window or tab >>Ionic Conducting Composite as Electrolyte forLow Temperature Solid Oxide Fuel Cells
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Solid oxide fuel cells (SOFCs) are considered as one of the most promising powergeneration technologies due to their high energy conversion efficiency, fuel flexibilityand reduced pollution. The current SOFCs with yttria-stabilized zirconia (YSZ)electrolyte require high operation temperature (800-1000 °C), which not only hinderstheir broad commercialization due to associated high cost and technologicalcomplications. Therefore, there is a broad interest in reducing the operating temperatureof SOFCs. The key to development of low-temperature SOFCs (LTSOFCs) is to explorenew electrolyte materials with high ionic conductivity at such low temperature (300-600 °C).Recently, ceria-based composite electrolyte, consisting of doped cerium oxide mixedwith a second phase (e.g. Na2CO3), has been investigated as a promising electrolyte forLTSOFCs. The ceria-based composite electrolyte has shown a high ionic conductivityand improved fuel cell performance below 600 °C. However, at present the developmentof composite electrolyte materials and their application in LTSOFCs are still at an initialstage. This thesis aims at exploring new composite systems for LTSOFCs with superiorproperties, and investigates conductivity behavior of the electrolyte. Two compositesystems for SOFCs have been studied in the thesis.In the first system, a novel concept of non-ceria-salt-composites electrolyte, LiAlO2-carbonate (Li2CO3-Na2CO3) composite electrolyte, was investigated for SOFCs. TheLiAlO2-carbonate electrolyte exhibited good conductivity and excellent fuel cellperformances below 650 oC. The ion transport mechanism of the LiAlO2-carbonatecomposite electrolyte was studied. The results indicated that the high ionic conductivityrelates to the interface effect between oxide and carbonate.In the second system, we reported a novel core-shell samarium-doped ceria(SDC)/Na2CO3 nanocomposite which is proposed for the first time, since the interface isdominant in the nanostructured composite materials. The core-shell nanocompositeparticles are smaller than 100 nm with amorphous Na2CO3 shell. The nanocompositeelectrolyte was applied in LTSOFCs and showed excellent performance. Theconductivity behavior and charge carriers have been studied. The results indicated that H+conductivity in SDC/Na2CO3 nanocomposite is predominant over O2- conductivity with1-2 orders of magnitude in the temperature range of 200-600 °C. It is suggested that theinterface in composite electrolyte supplies high conductive path for proton, while oxygenions are most probably transported by the SDC nano grain interiors. Finally, a tentativemodel “swing mechanism” was proposed for explanation of superior proton conduction.

Place, publisher, year, edition, pages
Royal institute of technology, 2010. 43 p.
Series
Trita-ICT/MAP AVH, ISSN 1653-7610 ; 2010:05
Identifiers
urn:nbn:se:kth:diva-24723 (URN)978-91-7415-670-6 (ISBN)
Presentation
2010-06-07, Electrum C2, Isajordsgatan 23, Kista, Stockholm, 16:27 (English)
Opponent
Supervisors
Note
QC 20100930Available from: 2010-09-30 Created: 2010-09-23 Last updated: 2010-09-30Bibliographically approved
2. 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)
Opponent
Supervisors
Funder
StandUp
Note

QC 20120529

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

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