The electrochemical performance of Metal Supported Solid Oxide Fuel Cells fabricated by co-firing with metal support, anode and electrolyte

Abstract

Energy problems is important issues because the consumption of a fossil fuel has dramatically increased. The depletion of fossil fuel reservation, air pollution by effluent gas emission and global warming are a few of identified problems. Solid oxide fuel cell (SOFC) is considered as a promising energy-conversion system due to its high electrical efficiency and environmentally friendly nature. Compared to the other types of fuel cells, SOFCs have superior properties in conversion efficiency, power density, stability, life time, and multi-fuel capability. However, current SOFCs are very weak against mechanical and thermal shocks because they have drawbacks, such as ceramic-inherent brittleness and low thermal conductivity.

Current unit cell of SOFCs have been commonly fabricated either electrolytesupported type or anode-supported type. Recently, metal-supported SOFC (MS-SOFC) has received high attention, because it can overcome the weakness of ceramics due to the good thermal and mechanical properties of metallic support. The commonly used materials used for the supporting metal are Fe Cr alloys including ferritic stainless steels (STSs), since they show good oxidation resistance, similar thermal-expansion coefficient (TEC) with YSZ (yittria-stabilized zirconia) electrolyte along with low price. To make SOFC be commercially competitive, it is necessary to reduce both the fabrication cost and raw material's cost. The fabrication of MS-SOFC by cost-efficient way can be the best way to serve both purposes. Co-firing of metal support / anode / electrolyte multilayer in reducing atmosphere can be an inexpensive, simple, and industrially route for the fabrication of MS-SOFC. The temperature is needed reaching up to 1300°C and 1400°C to achieve gas-tight dense zirconia electrolyte. And the anode and the metal support parts must be porous due to enough gas diffusion. In this research, the cell fabricated by 3 layer co-firing method; electrolyte, anode, and metal support was investigated. To get a desired design, sintering aid and pore former were used into the electrolyte, the anode and the metal support respectively. By using new binder system and new load for flat and fine surface of the cell, defects on the surface were reduce almost 95% down. The cell showed 1.11V OCV compared to theoretical value 1.13V and it proved that the microstructure of the cell was well designed. However, the power density was relatively lower than a cell which was made by thin film technique. By taking a look at voltage with high current and impedance pattern, it was possible that the anode and the cathode parts might have problem such as lower TPB area or not enough porosity, diffusion rate. So finding another sintering aid or changing the amount of pore former with various temperature can be one way to enhance the performance. Regarding to the reasonable results, fabricating the cell with 3-co firing method can be one candidate for effective process of the large MS-SOFCs.