Development and characterization of functional composite materials for advanced energy conversion technologies

• The solid oxide fuel cell (SOFC) is a potential high efficient electrochemical device for vehicles, auxiliary power units and large-scale stationary power plants combined heat and power application. The main challenges of this technology for market acceptance are associated with cost and lifetime due to the high temperature (700-1000 oC) operation and complex cell structure, i.e. the conventional membrane electrode assemblies. Therefore, it has become a top R&D goal to develop SOFCs for lower temperatures, preferably below 600 oC. To address those above problems, within the framework of this thesis, two kinds of innovative approaches are adopted. One is developing functional composite materials with desirable electrical properties at the reduced temperature, which results of the research on ceria-based composite based low temperature ceramic fuel cell (LTCFC). The other one is discovering novel energy conversion technology - Single-component/ electrolyte-free fuel cell (EFFC), in which the electrolyte layer of conventional SOFC is physically removed while this device still exhibits the fuel cell function. Thus, the focus of this thesis is then put on the characterization of materials physical and electrochemical properties for those advanced energy conversion applications. The major scientific content and contribution to this challenging field are divided into four aspects except the Introduction, Experiments and Conclusions parts. They are:Continuous developments and optimizations of advanced electrolyte materials, ceria-carbonate composite, for LTCFC. An electrolysis study has been carried out on ceria-carbonate composite based LTCFC with cheap Ni-based electrodes. Both oxygen ion and proton conductance in electrolysis mode are observed. High current outputs have been achieved at the given electrolysis voltage below 600 oC. This study also provides alternative manner for high efficient hydrogen production. Compatible and high active electrode development for ceria-carbonate composite electrolyte based LTCFC. A symmetrical fuel cell configuration is intentionally employed. The electro-catalytic activities of novel symmetrical transition metal oxide composite electrode toward hydrogen oxidation reaction and oxygen reduction reaction have been experimentally investigated. In addition, the origin of high activity of transition metal oxide composite electrode is studied, which is believed to relate to the hydration effect of the composite oxide.A novel all-nanocomposite fuel cell (ANFC) concept proposal and feasibility demonstration. The ANFC is successfully constructed by Ni/Fe-SDC anode, SDC-carbonate electrolyte and lithiated NiO/ZnO cathode at an extremely low in-situ sintering temperature, 600 oC. The ANFC manifests excellent fuel cell performance (over 550 mWcm-2 at 600 oC) and a good short-term operation as well as thermo-cycling stability. All results demonstrated its feasibility and potential for energy conversion.Fundamental study results on breakthrough research Single-Component/Electrolyte-Free Fuel Cell (EFFC) based on above nanocomposite materials (ion and semi-conductive composite) research activities. This is also the key innovation point of this thesis. Compared with classic three-layer fuel cells, EFFC with an electrolyte layer shows a much simpler but more efficient way for energy conversion. The physical-electrical properties of composite, the effects of cell configuration and parameters on cell performance, materials composition and cell fabrication process optimization, micro electrochemical reaction process and possible working principle were systematically investigated and discussed. Besides, the EFFC, joining solar cell and fuel cell working principle, is suggested to provide a research platform for integrating multi-energy-related device and technology application, such as fuel cell, electrolysis, solar cell and micro-reactor etc.This thesis provides a new methodology for materials and system innovation for the fuel cell community, which is expected to accelerate the wide implementation of this high efficient and green fuel cell technology and open new horizons for other related research fields.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Energiteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Energy Engineering (hsv//eng)

TEKNIK OCH TEKNOLOGIER  -- Nanoteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Nano-technology (hsv//eng)

TEKNIK OCH TEKNOLOGIER  -- Materialteknik -- Kompositmaterial och -teknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering -- Composite Science and Engineering (hsv//eng)

TEKNIK OCH TEKNOLOGIER  -- Materialteknik -- Keramteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering -- Ceramics (hsv//eng)

Nyckelord

Low temperature ceramic fuel cell

Ceria-carbonate composite

Electrolysis

Transition metal oxide

Symmetrical fuel cells

All-nanocomposite fuel cell

Electrolyte-free fuel cell

Solar cell

ion conductor and semiconductor

SRA - Energy

SRA - Energi

Publikations- och innehållstyp

vet (ämneskategori)

dok (ämneskategori)