Effect of Oxygen Depletion to the Cathode on the Working of Solid Oxide Fuel Cells

The performance of solid oxide fuel cells operating with varying oxygen concentrations, decreasing from an initial concentration of 21% (air), in the gas supplied to the cathode is investigated systematically. This is done by operating the cells at three different temperatures, namely 800, 850 and 900 degrees C. The performance is characterized by determining the I-V curves of the cells, whereby it is possible to roughly distinguish between ohmic losses and concentration losses. The most dramatic effects of decreasing the oxygen partial pressure to the cathode is found at oxygen concentrations below 12.6%, where the onset of concentration losses is seen to start to dominate at the highest current densities. After testing, it is found that the cells recovered their performance almost completely, when again supplied with air to the cathode, except in one case (the cell tested at 850 degrees C), where a threshold low oxygen concentration appears to have reached during the testing, causing the cell to recover less completely.