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Nanyang Technological University (NTU) - Singapore

Electrotechnical Institute Division of Electrotechnology and Materials Science in Wroclaw (IEL) - Poland

 

Solid Oxide Fuel Cells (SOFCs) offer a clean, pollution-free technology for the electrochemical generation of electricity with high efficiency. A typical SOFC operates near 1000 °C and utilizes yttrium-stabilised zircon (YSZ) as an electrolyte. This material exhibits an oxide-ion conductivity of about 0.1 Scm^-1 at 1000 °C.

 

One of the main objectives of the research should be to get significant improvements in performance of SOFC’s operating on logistic fuels (natural gas, biogas, hydrogen) by lowering their working temperature to intermediate temperatures (500-750 ºC).

 

The main innovation concept of the project is the use of new materials, new nano-structured architectures and/or compositions for the fabrication of electrochemical fuel cells, with the corresponding stack prototype system, that will allow to work at intermediate temperatures (IT-SOFC) using the direct oxidation of hydrocarbon fuels (i.e. CH₄, C₃H₅, C₄H₇) in the anode with high efficiency (> 60%). The hydrocarbon fuel could be modified (i.e. humidified at P_H2O < 60%) for softening the reducing anodic environment that could degrade some material and also for promoting the hydrocarbon oxidation. So, in this project we propose the study on synthesis, thermodynamic stability and electrochemcial, microstructural and mechanical characterization of selected ceramic materials. Two base electrolytes are to be investigated: ceria (GDC) and bismuth (BIMEVOX)-based solid electrolytes with transition metals and rare earth doping which exhibited ionic conductivities in the range of 0.1-1.0 S cm^-1 between 500-750°C. It is believed that these materials have high potential as electrolytes and electrodes in intermediate temperature solid oxide fuel cells for highly stable, low cost and low-emission power generation. Base on these materials the prototype stacks of intermediate temperature SOFC will be constructed. Very important for project realization will be establishing the influence of microstructure (grain boundaries, nano-micro grains size, porosity) of raw materials and sintered electrolyte and electrode ceramics on type (ionic or electronic) and value of conductivity and on catalytic parameters.

 

The first general strategy for nano-structuring ceramic layers and/or substrates is based on the generation of coherent nano-structures by sol-gel related or sputtering techniques. At present, it is possible the preparation of the above mentioned electrolytes and cathodes by the sol-gel related methods as: acrylamide, citrates, oxalates or pantadionates.

 

The second general strategyis to engineer nano-structured thin or thick layers of electrolytes or/and chemical barriers originated at the substrate interface (anode or electrolyte supported substrates). Dense interface thin films can be generated based on self-assembling principles induced by interfacial stress. So, it has been prepared successfully dense thin films of on ceramic and metal substrates by so-gel method. Chemical solution processing is chosen for SOFCs preparation, because high performance and low cost are combined.

 

The final technological objective of project is to prepare a prototype of fuel cell stack device based on intermediate temperature electrolytes (500-750ºC).