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Physico-Chemical and Electrochemical Properties of Sm0.075Nd0.075Ce0.85O2-δ Electrolyte Synthesized by Citrate-Nitrate Combustion for Intermediate-Temperature Solid Oxide Fuel Cells

Title
Physico-Chemical and Electrochemical Properties of Sm0.075Nd0.075Ce0.85O2-δ Electrolyte Synthesized by Citrate-Nitrate Combustion for Intermediate-Temperature Solid Oxide Fuel Cells
Authors
Chan Hoon Jung
DGIST Authors
Jung, Chan Hoon; Hong, Jong-Eun; Lee, Kang Taek
Advisor(s)
이강택
Co-Advisor(s)
Jong-Eun Hong
Issue Date
2019
Available Date
2020-02-28
Degree Date
2019-02
Type
Thesis
Abstract
Sm and Nd double-doped ceria (SNDC) has received significant attention in solid oxide fuel cells (SOFCs) because of its higher ionic conductivity compared to gadolinium-doped ceria (GDC), which is a singly-doped material. In this thesis, first, the physicochemical and electrochemical properties of SNDC electrolyte synthesized by citrate–nitrate combustion method were investigated. Dilatometry analysis confirmed that the sintering of SNDC was completed and saturated at 1400 oC, and the relative density result also showed a high value (~98%) at the same temperature. SNDC exhibited 27% higher (0.0495 S/cm) oxygen ionic conductivity than that of GDC at 700 oC, and the performance of SOFCs with an SNDC or GDC interlayer was compared. The results showed that SNDC had approximately 40% higher power density (0.99 W/cm-2) than that of the GDC single cell owing to the high ionic conductivity of SNDC and the improved oxygen reduction reaction (ORR) activity at the interface between the cathode and the SNDC interlayer. To reduce the sintering temperature of the SNDC, further research was carried out with the addition of 0.25–1.0 mol.% Cu (as a sintering aid). The sintering temperature of the SNDC was reduced by more than 300 oC, which was confirmed via dilatometry analysis. The prepared samples were subjected to electrochemical analysis1.0Cu-SNDC showed higher oxygen ionic conductivity than that of 0.5Cu-SNDC or 0.25Cu-SNDC. The 1.0Cu-SNDC diffusion barrier layer sintered at 1100 oC, which was lower than the conventional temperature of 1250 oC, possessed a higher density and better adhesion at the interface, which resulted in 9% higher performance compared to that of the SNDC cell.|Sm 과 Nd 이중 도핑 세리아 (SNDC)는 기존 단일 도핑 물질인 Gd 단일 도핑 세리아 (GDC) 보다 높은 이온전도도를 가지고 있는 고체산화물이며, 연료전지 분야에서 주목을 받고 있는 산소 이온 전도성 전해질이다. 본 연구에서는 첫째로, citrate-nitrate combustion 법으로 합성된 SNDC 전해질의 물리-화학적 및 전기화학적 특성을 연구 하였다. 열팽창 분석결과, SNDC는 1400 oC에서 전해질로서 물성이 가 장 우수하며, 동일한 온도대에서 측정된 상대 밀도가 98%이상의 높은 수치를 나타내었다. 산소 이온전도도 측정결과, SNDC는 GDC보다 27% 높은 수치를 기록하였으며, 두 전해질(SNDC와 GDC) 을 실제 고체산화물 연료전지 (SOFC) 확산방지층으로 적용하여 전기화학적 특성을 평가했다. 그 결과, SNDC 는 GDC 확산방지층 적용된 단전지보다 약 40% 높은 출력밀도를 나타내었으며, 이는 SNDC 의 높은 이온전도성, 확산방지층과 양극층 사이의 계면에서 향상된 산소 환원 반응 효과가 원인인 것으로 분석되었다. 위에 대한 추가 연구로서, SNDC의 문제점인 높은 소결온도를 해결하기위해, 소결조제인 Cu를 0.25-1.0 mol.% 첨가하여 SNDC 의 높은 소결온도를 낮추는 실험을 진행하였으며, 열팽창 분석을 통해 300 oC 이상 소결 온도가 낮아짐을 확인하였다. 전기화학 분석을 통해 1.0Cu-SNDC 가 가장 높은 산소이온전도도를 보여주는 것으로 나타났으며, 이를 확산방지층에 적용한 결과, Cu-SNDC는 기존(1250 oC)보다 낮은 소결온도(1100 oC)에서도 높은 밀도와 더불어YSZ 전해질과의 견고한 접착 을 보여주었으며, Cu가 첨가되지 않은SNDC 단전지보다 9% 높은 출력밀도를 나타내었다.
Table Of Contents
1. INTRODUCTION……………………………………………………………………...1 2. BACKGROUND INFORMATION…………………………………………………...3 2.1. FUNDAMENTAL OF SOLID OXIDE FUEL CELL……………………...……...3 2.2. PRINCIPLE OF PURE CERIUM OXIDE……………………………...…………4 2.3. DOPED CERIUM OXIDE………………………………………………………...5 2.4. CONDUCTIVITY DEPENDENT ON DOPANT SPECIES ……………………..5 3. CHARACTERIZATION OF SAMARIUM AND NEODYMIUM CO-DOPED CERIA SYNTHESIZED BY CITRATE-NITRATE COMBUSTION FOR SOLID OXIDE FUEL CELLS……………………………......................................................12 3.1. INTRODUCTION…………………………………………………………………12 3.2. EXPERIMENTAL PROCEDURE………………………………………………...13 3.3. RESULT AND DISCUSSION…………………………………………………….15 3.4. CONCLUSION……………………………………………………………………20 4. SINTERING BEHAVIOR AND ELECTRICAL PROPERTIES OF SAMARIUM AND NEODYMIUM CO-DOPED CERIA BY ADDITION OF SINTERING AID FOR SOLID OXIDE FUEL CELLS............................................................................34 4.1. INTRODUCTION…………………………………………………………………..34 4.2. EXPERIMENTAL PROCEDURE………………………………………………….35 4.3. RESULT AND DISCUSSION……………………………………………………...37 4.4. CONCLUSION………………………………………………………………….…..39 5. CONCLUSION………………………………………………………………………..47 6. REFERENCES………………………………………………………………………..49 7. 요약문………………………………………………………………………………….51
URI
http://dgist.dcollection.net/common/orgView/200000171518
http://hdl.handle.net/20.500.11750/10725
DOI
10.22679/thesis.200000171518
Degree
MASTER
Department
Energy Science&Engineering
University
DGIST
Files:
There are no files associated with this item.
Collection:
Department of Emerging Materials ScienceThesesMaster


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