Platinum-free, methane-fueled fuel cells developed
By Ben Coxworth
November 25, 2010
Reliable, affordable fuel cells have come not one but three steps closer to reality this week, with announcements from two research institutions regarding advances in the field. If the reported developments make their way into production, we could be seeing fuel cells that use more abundant, less expensive fuels and building materials, that are more consistent in their electricity production, and that have a lower operating temperature.
Along with his colleagues from Harvard University’s School of Engineering and Applied Sciences, Shriram Ramanathan has created all-ceramic thin-film solid-oxide fuel cells (SOFCs) that don’t contain any platinum. Traditionally, SOFCs require platinum-coated electrodes, which can be both expensive and unreliable – “If you use porous metal electrodes, they tend to be inherently unstable over long periods of time,” he explained. “They start to agglomerate and create open circuits in the fuel cells.”
In place of platinum, the solid oxides (ceramics) lanthanum strontium cobalt ferrite and yttria-stabilized zirconia were used.
The Harvard group has also created a micro-SOFC that draws its power from methane, and that has an operating temperature of less than 500 C (932 F). Traditionally, hydrogen has been the fuel source of choice for SOFCs, but methane is more abundant, cheaper, and requires less processing. Additionally, conventional SOFCs operate at a temperature of around 800 C (1,472 F). This limits their portability, requires them to be constructed from very heat-tolerant materials, and lengthens their start-up time.
“Low temperature is a holy grail in this field,” said Ramanathan. “If you can realize high-performance solid-oxide fuel cells that operate in the 300 C (572 F) range, you can use them in transportation vehicles and portable electronics, and with different types of fuels.”
Matthias Arenz in his lab at the University of Copenhagen (Photo: Jes Andersen/University of Copenhagen)
Should Ramanathan’s platinum-free cells have drawbacks, however, Matthias Arenz and his team at the University of Copenhagen have announced the next-best thing – fuel cells that use much less platinum than traditional cells.
In order to maximize its surface area, platinum is usually ground up into fine particles and applied to a carbon frame, which constitutes the fuel cell’s electrode. As Ramanathan pointed out, however, these particles can clump together over time. This causes them to lose surface area, which results in a weaker current.
Bigger particles would seem to be the answer, although these presumably require more platinum, and that stuff isn’t exactly given away. Clarkson University chemist Dan Goia, however, has created spheres out of a less costly metal, then just coated them with a thin layer of platinum. In experiments performed by Arenz, the larger “core shell catalyst” spheres were shown to create just as much electricity as the finer particles, but have so far shown no signs of agglomeration.
There’s just one catch – the “cheaper” material at the core of the spheres is gold. Needless to say, Arenz and Goia are now looking at using other materials to achieve the same results.