H[sub 2]S Poisoning of Solid Oxide Fuel Cells

The influence of fuel impurity on power generation characteristics of solid oxide fuel cells (SOFCs) has been analyzed by measuring cell voltage at a constant current density, as a function of concentration, operational temperature, and fuel gas composition. Reversible cell voltage change was observed around , while fatal irreversible degradation occurred at a lower operational temperature, at a higher concentration, and at a lower fuel ratio. Sulfur tolerance of SOFCs was improved by using -doped instead of -doped as electrolyte and/or as electrolyte component in the anode cermets. It has been found that poisoning consists of at least two stages, i.e., an initial cell voltage drop within a short time period to a metastable cell voltage, followed by a gradual larger cell voltage drop. Possible poisoning processes are discussed.