Solid oxide fuel cell performance under severe operating conditions

The performance and degradation of Solid Oxide Fuel Cells (SOFC) were studied under severe operating conditions. The cells studied were manufactured in a small series by ECN, in the framework of the EU funded CORE-SOFC project. The cells were of the anode-supported type with a double layer LSM cathode. They were operated at 750 °C or 850 °C in hydrogen with 5% or 50% water at current densities ranging from 0.25 A cm^–2 to 1 A cm^–2 for periods of 300 hours or more. The area specific cell resistance, corrected for fuel utilisation, ranged between 0.20 Ω cm² and 0.34 Ω cm² at 850 °C and 520 mV, and between 0.51 Ω cm² and 0.92 Ω cm² at 750 °C and 520 mV.

The degradation of cell performance was found to be low (ranging from 0 to 8%/1,000 hours) at regular operating conditions. Voltage degradation rates of 20 to 40%/1,000 hours were observed under severe operating conditions, depending on the test conditions.

Data analysis revealed a critical cell voltage of ca 750 mV, above which the degradation rates were trivial, but below which they were significant.

Some cells were also tested using a different procedure to that usually applied at Risø. This gave a different aging behaviour, indicating that the detailed test circumstances may be decisive to the outcome.