Researchers at The University of Texas at Austin have identified a material to make cheaper, longer-lasting fuel cells without compromising their energy production.
Fuel cells remain of interest to auto makers and manufacturers of electronic devices because they produce energy efficiently without directly adding to greenhouse gases in the atmosphere. The external source of fuel for fuel cells can also be quickly replaced in comparison to batteries, which require time to recharge.
However, use of fuel cells has been limited by engineering challenges that include the expense of platinum, the cells’ crucial component for converting chemical energy into electricity. Platinum can cost twice as much as gold.
The Journal of Physical Chemistry reported online this month (Nov. 12) that Mechanical Engineering Professor Arumugam “Ram” Manthiram and colleagues have successfully used a cheaper palladium alloy that matches platinum for its ability to produce electricity.
The researchers’ synthesized alloy effectively promotes one of the chemical reactions that occurs inside fuel cells to produce electricity. That reaction involves adding electrons to oxygen gas that has settled onto the surface of a fuel-cell electrode, a process called a reduction reaction. A material like platinum on the surface of an electrode is needed to promote (catalyze) the process in which paired oxygen atoms relinquish their tight bonds to each other and accept additional electrons.
“The alloy works slightly better than platinum for reducing gaseous oxygen,” said Manthiram, “and the alloy also provides a big advantage in terms of cost.”
Palladium is about five times cheaper than platinum because it is more readily available in the earth. And the palladium alloy is equally durable, an important feature in fuel cells, where chemical reactions take place at temperatures of 140 degrees Fahrenheit (60 degrees Celsius) or higher.
In the experiments led by Manthiram and postdoctoral fellow Vadari Raghuveer, they synthesized a palladium/cobalt/molybdenum alloy under conditions that included a temperature of 932 degrees Fahrenheit (500 degrees Celsius) to force the elements to intermingle. After verifying that the trio had formed an alloy using X-ray diffraction, they studied how well the material served as a catalyst on the reducing electrode (cathode) of a fuel cell.
The engineers and Professor of Chemistry and Biochemistry Allen Bard determined the alloy had two advantages. It not only worked as well as a platinum-based cathode, but took longer to degrade and lose catalytic ability when methanol fuel was used as the source of electrons for reduction reactions.
Many of the investigator’s experiments have focused on gaseous hydrogen fuel as the source of fuel-cell electrons, as would be used in the stacks of fuel cells that could one day power cars. However, they also studied methanol because electronic devices such as laptops and cell phones are being commercialized that use a methanol-powered fuel cell.
“Our new material has the commercial prospect of being able to work in fuel cells that power all of these emerging technologies,” said Manthiram, who holds the Ashley H. Priddy Centennial Professorship in Engineering.
Bard holds the Norman-Hackerman Welch Regents Chair in Chemistry, and led a previous study with Manthiram about a palladium/cobalt/gold alloy that started the current investigation. The previous study was published in the Sept. 28 issue of the Journal of the American Chemical Society. Raghuveer will soon begin a second postdoctoral fellowship at the New Mexico State University.
For photos of the study participants, go to: www.engr.utexas.edu/news/action_shots/pages/manthiram.cfm
This research was funded by grants from the Welch Foundation and National Science Foundation.
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