Investigation of Clad Metals for Use as Bipolar Plate Material in PEM Fuel Cell Stacks
Although metal interconnects offer many advantages over their carbon-based counterparts, they suffer from surface corrosion which 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 graphite electrode backing. The approach currently under development employs an inexpensive clad metal laminate as the primary material for the bipolar plate. The key in making this work is in identifying an appropriate surface passivation layer that mitigates corrosion while at the same time allows for good electronic conduction. The current study investigated the kinetics of nitride formation on Nb and Ti foils as a function of time, temperature, atmosphere (N2-H2 gas composition), and the corrosion behavior. These two metals are being considered for use as a thin external cladding layer over an inexpensive steel core layer. As the nitride layer formation temperature was increased, the surface morphologies for both niobium and titanium substrates became coarser and more pitted, the nitride thicknesses of both increased non-linearly, and in the titanium system an oxide layer product layer on the outer surface grew as well. As the isothermal hold time was increased, the surface morphologies of both niobium and titanium reaction product layers did not change noticeably, and the thicknesses of the nitride layers increased. As the amount of hydrogen in the atmosphere was increased the surface morphologies for both the niobium and titanium did not change detectably, the thicknesses of the nitride layers increased, and titanium thicknesses of the oxide layers decreased. The nitrided niobium exhibited much better corrosion behavior than the nitrided titanium but no improvement was obtained relative to the pure Nb corrosion rates.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 947943
- Report Number(s):
- PNNL-SA-50962; HI0300000; TRN: US200905%%320
- Resource Relation:
- Conference: Materials Science & Technology 2006: Fuel Cells and Energy Storage Systems: Materials, Processing, Manufacturing and Power Management Technologies, 165-178
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
25 ENERGY STORAGE
30 DIRECT ENERGY CONVERSION
36 MATERIALS SCIENCE
CATALYSTS
CORROSION
ELECTRODES
ELECTROLYTES
ENERGY STORAGE SYSTEMS
FUEL CELLS
GRAPHITE
HYDROGEN
KINETICS
MEMBRANES
NIOBIUM
NITRIDES
OXIDES
PASSIVATION
PLATES
SUBSTRATES
TITANIUM
PEM fuel cell
bipolar plate
clad metal
ntridation