High-Temperature Polymer Electrolyte Fuel Cells: Durability Insights

Abstract

BASF Fuel Cell (formerly PEMEAS) produces polybenzimidazole-based high-temperature membrane electrode assemblies (MEAs). These Celtec®-P MEAs operate at temperatures between 120 and 180°C, and, therefore, are especially suitable for use in reformed-hydrogen-based polymer electrolyte fuel cells. Owing to these high operating temperatures, CO tolerances up to 3% can be achieved. Additional fuel gas impurities (inorganic or organic) can be tolerated to a much higher concentration than in low-temperature fuel cells. From a fuel cell system perspective, waste heat can be effectively used which increases the overall system efficiency. However, besides the distinct advantages over low-temperature polymer electrolyte fuel cells, some challenges have to be overcome. Especially on the catalyst level, there are several requirements which have to be met. In detail these are (1) anode catalyst activity for the oxidation of CO in the presence of hydrogen, (2) cathode catalyst activity in the presence of an adsorbing electrolyte such as phosphoric acid, and (3) high corrosion stability of the catalyst metal and catalyst support, especially under transient operation conditions such as start/stop or local fuel starvation. Especially the last point is important since for successful commercialization of MEAs, durability, reliability, and robustness are critical factors. That is, all materials used in MEAs have to be highly durable even under nonideal daily life conditions outside the laboratory. This contribution gives insight into the degradation mechanism during start/stop operation. Several tests are presented giving a better understanding of corrosion effects in high-temperature MEAs.