Carl A. Reiser

Systems Strategies to Mitigate Carbon Corrosion in Fuel Cells

The oxidation of carbon used as catalyst support in state-of- the art fuel cells is a serious decay mechanism that must be mitigated in order to achieve acceptable performance stability. Although the corrosion of carbon is certainly not a new concern for fuel-cell developers, a number of fairly recent developments have brought this issue to the forefront. These concerns include the unique operating conditions of transportation applications, the discovery of a mechanism that results in higher-than-expected potentials (i.e., the reverse- current mechanism), and the use of certain materials (e.g., high surface area carbon supported catalysts with high Pt mass fractions). Since improvements in catalyst-support stability typically comes at the expense of performance (and/or cost), and these improvements alone will be insufficient for many applications, system-mitigation strategies are required. A number of system strategies that have been developed and demonstrated at UTC Power will be described.

Operating Requirements for Durable Polymer-Electrolyte Fuel Cell Stacks

Successful developers of fuel cells have learned that the keys to achieving excellent durability are controlling potential and temperature, as well as proper management of the electrolyte. While a polymer-electrolyte fuel cell (PEFC) has inherent advantages relative to other types of fuel cells, including low operating temperatures and an immobilized electrolyte, PEFC stacks also have unique durability challenges owing to the intended applications. These challenges include cyclic operation that can degrade materials owing to significant changes in potential, temperature, and relative humidity. The need for hydration of the membrane as well as the presence of water as both liquid and vapor within the cells also present complications. Therefore, the development of durable PEFC stacks requires careful attention to the operating conditions and effective water management.