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Highly Active and Thermally Stable Perovskite Electrocatalysts Synthesized by in-situ Infiltration Process for High-Temperature Solid Oxide Cells

Infiltration을 통한 고온 고체 산화물 전지용 고활성 perovskite 전기 촉매 합성 기술 개발

  • MiYoungPark (박미영, 대학원 신소재공학과 신소재공학전공)

초록/요약

Solid oxide fuel cells (SOFCs) represent one of the most efficient and versatile means of converting the chemical energy of fuel into electric power. Thus far, significant research efforts have been devoted to utilizing nanotechnologies to improve its activity, but nanomaterials are not usually stable at high temperatures and readily cause cell failure. To harness the high activity of nanomaterials while ensuring the structural integrity of the framework, herein, an advanced “infiltration” technique that synthesizes highly active and thermally stable perovskite nanocatalysts was developed. It was discovered that the presence of impurity phases causes the abnormality of nanoparticles at elevated temperatures, and accordingly, the formation of pure single-phase multicomponent oxides imparted these nanomaterials with excellent controllability and thermal stability. Using complexing agents optimized for individual cations enabled the formation of single-phase perovskite at lower processing temperatures and produced extremely small and homogeneously distributed nanoparticles. This technique was applied to commercial cell platform and more than doubled the main performance metrics. Furthermore, the elaborate control of the chemical and geometric properties of electrocatalysts enabled the construction of novel electrode structure featuring the thin electronic conduction region over the surface of ion-conductive scaffold, which produced extremely high cell performance. The key findings of this study can resolve the critical issues hindering the high-temperature application of various nanotechnologies and accelerate the commercialization of SOFC technology.

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목차

ABSTRACT I
국문 초록 III
TABLE OF CONTENTS V
LIST OF TABLES VIII
LIST OF FIGURES IX
NOMENCLATURE XV
CHAPTER 1. INTRODUCTION １
1.1 Overview of fuel cells １
1.1.1 Fundamentals of fuel cells １
1.1.2 Types of fuel cells ３
1.2 Solid Oxide Fuel Cells (SOFCs) ４
1.2.1 Characteristics of SOFCs ４
1.2.2 Challenges ６
1.2.3 Performance of SOFC (polarization losses) ７
1.3 Infiltration technique for the synthesis of nanocatalysts ９
1.4 Thermal behavior of nanocatalysts １１
1.5 Scope of the thesis １３
CHAPTER 2. EXPERIMENTAL １４
2.1 Synthesis of powder catalysts １４
2.2 Fabrication and characterization of symmetric cells １５
2.2.1 Standard half cells based on La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) and gadolinia-doped ceria (GDC) １５
2.2.2 Half cells based on ionic conducting skeleton １６
2.3 Fabrication and characterization of full cells １７
2.3.1 Standard cells １７
2.3.2 Advanced cells with novel electrode design １７
2.4 Fabrication and characterization of large-scale cells １８
CHAPTER 3. RESULTS AND DISCUSSION １９
3.1 Low-temperature synthesis of phase-pure perovskite nanocatalysts via infiltration １９
3.1.1 Synthesis of phase-pure SSC nanocatalysts. ２０
3.1.2 Electrochemical characteristic of symmetric cells ３４
3.1.3 Electrochemical characteristic of full cells (2x2, 1cm2) ４０
3.1.4 Electrochemical characteristic of large-scale cell (12x12, 100cm2) ４７
3.2 Novel electrode design based on infiltrated perovskite nanoparticles on the surface of oxygen ion-conducting scaffold ５３
3.2.1 Effect of loading content of SSC nanoparticles on electrochemical performance ５６
3.2.2 Electrochemical characteristic of symmetric cell ５９
3.2.3 Performance evaluation of full cell ６１
3.3 Novel electrode design using based on perovskite thin film over the surface of oxygen ion-conducting scaffold ６５
3.3.1 Effect of heat treatment temperature on electrode morphology ６６
3.3.2 Electrochemical characteristics of full cell ６８
3.3.3 Evaluation of scale-up capability ７２
CHAPTER 4. CONCLUSIONS & FURTURE WORK ７３
4.1 Conclusions ７３
4.2 Future work ７５
REFERENCES ７６

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