Performance of IT-SOFC with Ce0.9Gd0.1O1.95 Functional Layer at the Interface of Ce0.9Gd0.1O1.95 Electrolyte and Ni-Ce0.9Gd0.1O1.95 Anode

✍ Scribed by J. S. Ahn; H. Yoon; K. T. Lee; M. A. Camaratta; E. D. Wachsman

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 490 KB
• Volume: 9
• Category: Article
• ISSN: 1615-6846
• DOI: 10.1002/fuce.200900005

✦ Synopsis

For localised power plants, intermediate temperature solid oxide fuel cell (IT-SOFCs) are more advantageous than high temperature SOFCs [1]. The lowering of SOFC operating temperatures has been aided by the adoption of electrolytes based on doped ceria which has higher ionic conductivity than doped zirconia. Utilisation of doped ceria electrolytes with thicknesses below 15 lm significantly reduces ohmic polarisation losses at temperatures between 500 and 600 °C [2]. In order to fabricate stacked, large diameter planar SOFCs with doped ceria electrolytes, it is crucial to prepare a dense and thin ceria electrolyte layer on the anode. Tape casting is widely used for planar and multi-stacked ceramic devices because it is a reproducible and efficient ceramic fabrication process. Planar SOFCs have attractive geometries for simple stacking integration. Tape casting of anode supports combined with colloidal deposition of electrolytes is cost-effective and suitable for mass production.

For high performance at intermediate temperature, the electrode reactions are also important. Most SOFC electrode reactions take place at triple phase boundaries (TPB) between the gas phase, an electronic conducting phase and an ionic conducting phase. Increasing these TPB lengths increases the number of active reaction sites and therefore enhances the performance of SOFCs. Deposited on an electrolyte of a given surface area, electrodes composed of smaller particles result in larger TPB lengths. Therefore, it is clear that use of smaller particles for the electrode will result in better SOFC performance. However, while smaller particles produce higher TPB lengths, they tend to increase density. It is difficult for a dense anode to provide fuel rapidly to the reaction sites and to remove water molecules efficiently.