Sulfur Poisoning of Ni Anode as a Function of Operating Conditions in Solid Oxide Fuel Cells

Abstract

In the present study, we investigated the sulfur poisoning of the Ni anode in solid oxide fuel cells (SOFCs) as a function of operating conditions. Anode supported cells were fabricated, and sulfur poising tests were conducted as a function of current density, H2S concentration and humidity in the anode gas. The voltage drop was significant under the higher current density (~ 714 mA/cm2) condition, while it was much reduced under the lower current density (~ 389 mA/cm2) condition, at 100 ppm of H2S. A secondary voltage drop, which ℃curred only at the high current density, was attributed to Ni oxidation in the anode. Thus, operation at high current density with high H2S concentration may lead to permanent deterioration in the anode. The effect of water content (10%) on the sulfur poisoning was also investigated through a constant current test (~ 500 mA/cm2) at 10 ppm of H2S. The cell operating with 10% wet anode gas showed a much smaller initial voltage drop, in comparison with a dry anode gas. The present study indicates that operating conditions, such as gas humidity and current density, should be carefully taken into account, especially when fuel cells are operated with H2S containing fuel. Key words: solid oxide fuel cells, degradation, alternative fuel, sulfur poisoning