Plasma Sprayed Metal Supported SOFCs having Enhanced Performance and Durability

Kurzfassung

German Aerospace Center Centre (DLR) is developing an innovative concept of solid oxide fuel cell (SOFC) which is based on depositing functional layers (anode, electrolyte, and cathode) on porous metal substrate using plasma spraying. It is, therefore, referred as the metal supported-SOFC (MSSOFC). The conventional materials and plasma spraying approaches resulted in cells exhibiting poor power densities of around 180 mW/cm² and more than 7% / 1000 h degradation rates when operating at 800°C. By systematic improvement in the processing conditions, incorporating sub-micrometer-sized or nanometer-sized functional electrodes and introducing additional functional layers to prevent interlayer diffusions, higher performance and durability of cells was achieved. At 800°C, our latest generation cells exhibited more than 750 and 520 mW/cm² respectively with 0.08 slm/cm² H2 and 0.16 slm/cm² O2 and 0.04 slm/cm² H2 + 0.04 slm/cm² N2 and 0.16 slm/cm² air as fuel and oxidizing gases. The OCV was 1.1 V which is the highest reported value for plasma sprayed cells and is comparable to that of sintered cells. Static electrochemical test for 1500 hours was performed with degradation rate less than 3% / 1000 h. Redox stability of these cells was demonstrated for 20 cycles where anodes were fully oxidized. Up-scaling to larger (90×120 mm²) substrates initially resulted in detrimental distortion of metal supports owing to heat transfer and momentum transfer from plasma jet and molten particles to substrates. These problems were successfully overcome.