Development and optimization of porous carbon papers suitable for gas diffusion electrodes. Final report, December 2000 Page: 2 of 18

                                
DE-FC02-97EE50474

Program Summary
Objectives
* The primary objectives of this program were improved performance and cost
reduction in polymer electrolyte membrane (PEM) fuel cells through the
optimization of the carbon based gas diffusion electrode (GDE) material. A
matrix of numerous variations in the composition and processing of carbon fiber
based papers was to be designed, manufactured, and fuel cell tested to determine
the effect of performance enhancing and lower cost materials and processes.
Approach
" Various parameters in carbon/carbon GDE such as pore size distribution,
electrical and thermal conductivity, and compression strength were to be changed
by varying fiber types and lengths, heat treatment temperatures, density, and
thickness (over 30 variants).
" Fuel cell performance testing was to be conducted on the manufactured GDE
matrix. Subsequent analysis would correlate changes in GDE parameters to
changed in fuel cell performance. The most promising GDE variants were to be
subjected to longer term fuel cell testing to confirm initial results.
- The optimized paper(s) were to be manufactured on production equipment and
made available for evaluation by laboratory and industry partners.
Accomplishments
" A matrix of over 30 GDE variants was designed, manufactured and tested for
physical and electrical properties as well as pore size, pore size distributions and
gas flow.
" Initial fuel cell testing eliminated most variants using cost and performance
criteria. Several lower heat treatment (and hence lower cost) variants that were
not anticipated to perform well equaled the fuel cell performance of industry
standard GDE materials.
i Longer term fuel cell testing was performed on the more promising variants from
initial screening tests. Initial results on the lower heat treatment materials were
confirmed, demonstrating the feasibility of lower cost materials and
manufacturing techniques, as well as the possibility of manufacturing carbon
paper based GDE's in continuous rolls
- Based on the fuel cell testing results, a batch of a thinner, lower heat treatment
GDE was manufactured utilizing production equipment and has been made
available to DOE's government and industry partners.
" Several preliminary trials have been conducted towards the development of a
continuous process resulting in a continuous roll of carbon fiber paper based GDE
material. Initial results look promising and will be pursued in future
development.

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