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postgraduate thesis: Synthesis and structure optimization of gadolinium doped ceria-platinum composite for intermediate temperature solid oxide fuel cellcathode

TitleSynthesis and structure optimization of gadolinium doped ceria-platinum composite for intermediate temperature solid oxide fuel cellcathode
Authors
Advisors
Advisor(s):Chan, GKY
Issue Date2012
PublisherThe University of Hong Kong (Pokfulam, Hong Kong)
Citation
Yung, H. [容海]. (2012). Synthesis and structure optimization of gadolinium doped ceria-platinum composite for intermediate temperature solid oxide fuel cell cathode. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b4819926
AbstractSolid oxide fuel cells (SOFC), owing to its high operating temperatures, have many advantages over other types of fuel cells. Its commercialization, however, relies greatly on its costs and long term durability. By reducing the operating temperature to the intermediate temperature range, the costs for the balance of plant would be significantly reduced. The greatest contribution to cell over-potential at this temperature range is the oxygen reduction at cathode; hence development of a cathode material with low specific resistance and durability would have direct impact on the commercialization of SOFC. Composite cathode is a common strategy used by many to improve cathode performance. This was done conventionally by random mixing of cathode material with a better ionic conductor such as the electrolyte material. Impregnation or infiltration is often used to improve interconnectivity among individual phases in the composite, In this study, fabrication of a composite cathode with two phases - gadolinium doped ceria (GDC) and platinum attempted, forming two inter-locked networks each with a channel dimension in the nanometer range by hard templating and chemical vapor infiltration (CVI) both for the first time to the best of my knowledge. It was found that surface layer of these materials play a very important role in the performance and structural stability. Another set of composite cathode was fabricated by packing commercially available GDC with carbon pore-former following by impregnation with Pt/Ag-Pt alloy. By introducing small amount of silver (6wt%), area specific resistance of 0.94cm2 and 0.16cm2 were observed at 550C and 660C, respectively during impedance spectroscopy in symmetrical cell arrangement. Silver was proposed to provide greater effective surface area for surface exchange and extending the triple phase boundary. Platinum was also suggested to provide a surface where silver wetting is possible stabilizing morphology of silver in the GDC scaffold. Platinum is not a practical choice of electrode material due to its costs and lower performance, it was chosen to demonstrate the strategy of vapor phase infiltration in fabricating SOFC composite cathode. However, the technique of CVI demonstrated can potentially be applied to other cathode candidate materials.
DegreeDoctor of Philosophy
SubjectGadolinium.
Platinum.
Fuel cells.
Dept/ProgramChemistry

 

DC FieldValueLanguage
dc.contributor.advisorChan, GKY-
dc.contributor.authorYung, Hoi.-
dc.contributor.author容海.-
dc.date.issued2012-
dc.identifier.citationYung, H. [容海]. (2012). Synthesis and structure optimization of gadolinium doped ceria-platinum composite for intermediate temperature solid oxide fuel cell cathode. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b4819926-
dc.description.abstractSolid oxide fuel cells (SOFC), owing to its high operating temperatures, have many advantages over other types of fuel cells. Its commercialization, however, relies greatly on its costs and long term durability. By reducing the operating temperature to the intermediate temperature range, the costs for the balance of plant would be significantly reduced. The greatest contribution to cell over-potential at this temperature range is the oxygen reduction at cathode; hence development of a cathode material with low specific resistance and durability would have direct impact on the commercialization of SOFC. Composite cathode is a common strategy used by many to improve cathode performance. This was done conventionally by random mixing of cathode material with a better ionic conductor such as the electrolyte material. Impregnation or infiltration is often used to improve interconnectivity among individual phases in the composite, In this study, fabrication of a composite cathode with two phases - gadolinium doped ceria (GDC) and platinum attempted, forming two inter-locked networks each with a channel dimension in the nanometer range by hard templating and chemical vapor infiltration (CVI) both for the first time to the best of my knowledge. It was found that surface layer of these materials play a very important role in the performance and structural stability. Another set of composite cathode was fabricated by packing commercially available GDC with carbon pore-former following by impregnation with Pt/Ag-Pt alloy. By introducing small amount of silver (6wt%), area specific resistance of 0.94cm2 and 0.16cm2 were observed at 550C and 660C, respectively during impedance spectroscopy in symmetrical cell arrangement. Silver was proposed to provide greater effective surface area for surface exchange and extending the triple phase boundary. Platinum was also suggested to provide a surface where silver wetting is possible stabilizing morphology of silver in the GDC scaffold. Platinum is not a practical choice of electrode material due to its costs and lower performance, it was chosen to demonstrate the strategy of vapor phase infiltration in fabricating SOFC composite cathode. However, the technique of CVI demonstrated can potentially be applied to other cathode candidate materials.-
dc.languageeng-
dc.publisherThe University of Hong Kong (Pokfulam, Hong Kong)-
dc.relation.ispartofHKU Theses Online (HKUTO)-
dc.rightsThe author retains all proprietary rights, (such as patent rights) and the right to use in future works.-
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License-
dc.source.urihttp://hub.hku.hk/bib/B48199266-
dc.subject.lcshGadolinium.-
dc.subject.lcshPlatinum.-
dc.subject.lcshFuel cells.-
dc.titleSynthesis and structure optimization of gadolinium doped ceria-platinum composite for intermediate temperature solid oxide fuel cellcathode-
dc.typePG_Thesis-
dc.identifier.hkulb4819926-
dc.description.thesisnameDoctor of Philosophy-
dc.description.thesislevelDoctoral-
dc.description.thesisdisciplineChemistry-
dc.description.naturepublished_or_final_version-
dc.identifier.doi10.5353/th_b4819926-
dc.date.hkucongregation2012-

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