Event
MSE Seminar - Dr. Eric D. Wachsman, UMERC Director, University of Maryland
Friday, September 25, 2009
1:00 p.m.
Room 2108, Chemical and Nuclear Engineering Bldg.
Annette Mateus
301 405 5207
amateus@umd.edu
"Development of a Lower Temperature SOFC"
There has been a tremendous effort to lower the operating temperature of solid oxide fuel cells (SOFC) to ≤800?C, for cost and reliability considerations; while simultaneously there has been an even larger effort to increase the operating temperature of proton exchange membrane fuel cells (PEMFC) to >100?C, for performance and fuel poisoning considerations. Somewhere in between is the optimum operating temperature for a fuel cell depending on fuel choice and degree of external fuel processing (vs. relying exclusively on internal reforming). To date there has been limited success at obtaining a PEM electrolyte capable of operating in this temperature range.
In contrast, alternate higher conductivity, and thus lower temperature, oxide electrolytes have existed for some time (ranging from gallates and ceria to bismuth oxide based materials). However, each of these materials has it's own specific issues. Moreover, transitioning from a zirconia electrolyte to one of these alternate electrolytes requires development of an entirely new cell material set.
Over the last 20 years we have focused on using the most conductive, and hence lowest temperature, bismuth oxide based electrolyte. To overcome its inherent instability in reducing environments we developed a bilayer bismuth-oxide/ceria electrolyte. To overcome reactivity with more conventional cathode materials we developed a bismuth-ruthenate/bismuth-oxide composite cathode. Finally, these materials were integrated into an anode supported cell resulting in power densities of ~2 W/cm2 at 650?C.
The materials issues, how they were addressed, and the ultimate performance achieved will be discussed.
