Development of Low-Cost, Clad Metal Bipolar Plates for PEM Fuel Cells
The bipolar plate is the most bulky component in the PEMFC stack (in both weight and volume) and one of the most expensive to manufacture. It serves not only as the electrical junction between serially connected cells, but also performs several other key functions in the device: • Distribute the fuel and oxidant uniformly over the active areas of the cells. • Facilitate water management of the membrane to keep it humidified, yet mitigate flooding. • Act as an impermeable barrier between the fuel and oxidant streams (particularly H2) to maintain the hydrogen gradient across the membrane necessary for high power output. • Provide some measure of structural support for the stack. • Remove heat from the active areas of the cells. The use of metal-based bipolar plates in PEMFC stacks potentially offers a number advantages particularly for transportation applications including: low-cost, mass-production via stamping or embossing of sheet product; fabrication in very thin form (< 200μm) to reduce weight and volume in the overall stack; impermeability to fuel, oxidant and water vapor; and in general, excellent thermal conduction properties and good mechanical robustness, even as a thin stamped foil. The primary challenge with metal interconnects is surface corrosion, and the current drive to increase the operating temperature of the stack will only exacerbate this problem. Corrosion of the bipolar plate leads to a release of metal ions that can contaminate the electrolyte membrane and poison the electrode catalysts. In addition, the formation of a passivating oxide or oxyhydroxide layer on the surface of the metal will increase the contact resistance between the bipolar plate and the adjacent graphite electrode backing layer by many orders of magnitude. Both conditions can significantly degrade stack performance. A number of researchers have investigated various schemes for protecting metallic bipolar plates, most of which rely on a thin, inert yet electrically conductive coating [1]. The greatest level of success that has been openly reported has been achieved with noble metal coatings such as gold and palladium. Unfortunately commercial use of these materials, even as thin coatings, is cost prohibitive.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1059637
- Report Number(s):
- PNNL-SA-46088; HI0300000
- Country of Publication:
- United States
- Language:
- English
Similar Records
PEM fuel cell bipolar plate material requirements for transportation applications
Corrosion resistant PEM fuel cell