The performance of single-cell planar solid oxide fuel cells using coal syngas, with and without hydrogen sulfide (H2S), was studied. A state-of-the-art gas delivery system, data acquisition system, and test stand were designed and assembled for experimentation. All cells were tested at 850 degrees C with a constant current load of 14.3 A (current density of 0.20 A cm(-2)). The results from using syngas with no H2S indicated no degradation after 290 h of operation. After immediately injecting CO (and water) in the H-2-N-2 mixture, there was a slight tendency of improving performance (power) and then the behavior remained steady. On the other hand, results for the test with syngas in the presence of H2S (200-240 ppm) indicated good performance over 570 h (650 h total operation time) with 10-12.5% degradation. The results suggest these cells can be used for extended periods of time for syngas applications, and in the presence of H2S the cells show no major degradation. (c) 2005 Elsevier B.V. All rights reserved.